Families gathering around the dinner table on Thanksgiving enjoy a common food culture: roasted turkey, sweet cranberry sauce, succulent squash, fluffy stuffing, buttery potatoes, and freshly baked pumpkin pie. It's the oldest menu Americans know, and perhaps because we're aware of its origins, we don't often think about the chemistry of its components or about how science can heighten our Thanksgiving experience.

On NOVA scienceNOW's "Can I Eat That," premiering October 31, David Pogue, with the help of America's Test Kitchen, uses a dash of science to prepare several Thanksgiving dinners to ensure that everyone is full and happy by the end of the meal. Below are the exact recipes used in the show. You can use them as basic guidelines to the iconic Thanksgiving dinner, or in the interest of variety, as inspiration to deviate a little from traditional fare (via international examples or unusual twists on old favorites).

The Test Kitchen crew focused on the chemical properties of onions, turkey, and stuffing independent of one another. But to many food mixers and mashers, flavor pairing is more cutting-edge terrain. It can help answer such perennial questions as: Why does everything on the Thanksgiving table taste so good together? And why is this particular combination so satisfying?

Last December, Scientific Reports published a study that hypothesized that ingredients sharing flavor compounds are more likely to taste yummy together than ingredients that do not. Although the paper's authors acknowledged that "the scientific analysis of any art, including the art of cooking, is unlikely to be capable of explaining every aspect of the artistic creativity involved," and that how food is prepared plays an important role, they claimed that some basic flavor traits might supersede those factors.

Their "flavor network," which you can view by following this link, reveals some not-so-surprising facts about Thanksgiving food. Though cranberries and turkey are not directly connected, certain meats share flavor compounds with wine, which in turn shares flavor compounds with various fruits. Meats have strong ties to potatoes, onions, yeast, and beans. Cucumbers--which, like pumpkin and squash, belong to the Cucurbitaceae family of vegetables--share flavor compounds with butter, which is connected to meats and wheat. And it seems that apples, too, closely resemble wine in their composition.

The flavor network map exposes the way some parts of Thanksgiving dinner open up the palate and make the meal less monochromatic. Spices in pumpkin pie--cinnamon, nutmeg, cloves, and allspice--cluster in one part of the schematic near nuts, herbs, flowers, and a few vegetables but away from most of the meal's ingredients. The same holds true for cranberry sauce, which has close ties with other fruits, kelp, and some of seafood. The map might also explain optional side dishes, like shrimp, cheese dishes, and citrus elements; orange is the only fruit on the map that shares flavor compounds with nutmeg. Which brings us to the post-meal food coma. According to the study's flavor network, tea and coffee tie together the various Thanksgiving food groups--meats, spices, and alcohol. Fittingly--and perhaps unwittingly--our after-dinner customs may help tie everything together.

With the food map as a guide, you can start to concoct your own Thanksgiving meal, perhaps one with an Asian-American flair, which would balance the Western practice of pairing ingredients with shared flavor compounds with the Eastern tradition of using ingredients with more disparate flavor compounds. Such mixing and matching may be why tabouli tastes so good--its ingredients (wheat, lemon, tomato, and parsley) are scattered across the map, but all have ties to more centered ingredients like tea.

Recipes for a NOVA scienceNOW Thanksgiving

ROASTED BRINED TURKEY

Serves 10-12

This recipe is designed for a natural turkey, not treated with salt or chemicals. If using a self-basting turkey (such as a frozen Butterball) or kosher turkey, do not brine in step 1, and season with salt after brushing with melted butter in step 5. Resist the temptation to tent the roasted turkey with foil while it rests on the carving board. Covering the bird will make the skin soggy.

1 cup salt
1 (12- to 14-pound) turkey, neck, giblets, and tailpiece removed and reserved for gravy
2 onions, chopped coarse
2 carrots, peeled and chopped coarse
2 celery ribs, chopped coarse
6 sprigs fresh thyme
3 tablespoons unsalted butter, melted
1-1 1/2 cups water
1 recipe Giblet Pan Gravy

1. Dissolve salt in 2 gallons cold water in large container. Submerge turkey in brine, cover, and refrigerate or store in very cool spot (40 degrees or less) for 6 to 12 hours.

2. Set wire rack in rimmed baking sheet. Remove turkey from brine and pat dry, inside and out, with paper towels. Place turkey on prepared wire rack. Refrigerate, uncovered, for at least 8 hours or overnight.

3. Adjust oven rack to lowest position and heat oven to 400 degrees. Line V-rack with heavy-duty aluminum foil and poke holes in foil. Set V-rack in roasting pan and spray foil with vegetable oil spray.

4. Toss half of onions, half of carrots, half of celery, and thyme with 1 tablespoon melted butter in bowl and place inside turkey. Tie legs together with kitchen twine and tuck wings behind back. Scatter remaining vegetables in pan.

5. Pour water over vegetable mixture in pan. Brush turkey breast with 1 tablespoon melted butter, then place turkey breast side down on V-rack. Brush with remaining 1 tablespoon butter.

6. Roast turkey for 45 minutes. Remove pan from oven. Using 2 large wads of paper towels, turn turkey breast side up. If liquid in pan has totally evaporated, add another 1/2 cup water. Return turkey to oven and roast until breast registers 160 degrees and thighs register 175 degrees, 50 minutes to 1 hour.

7. Remove turkey from oven. Gently tip turkey so that any accumulated juices in cavity run into pan. Transfer turkey to carving board and let rest, uncovered, for 30 minutes. Carve turkey and serve with gravy.

GIBLET PAN GRAVY

Makes about six cups

Complete step 1 up to a day ahead, if desired. Begin step 3 once the bird has been removed from the oven and is resting on a carving board.

1 tablespoon vegetable oil
Reserved turkey giblets, neck, and tailpiece
1 onion, chopped
4 cups low-sodium chicken broth
2 cups water
2 sprigs fresh thyme
8 sprigs fresh parsley
3 tablespoons unsalted butter
¼ cup all-purpose flour
1 cup dry white wine
Salt and pepper

1. Heat oil in Dutch oven over medium heat until shimmering. Add giblets, neck, and tailpiece and cook until golden and fragrant, about 5 minutes. Stir in onion and cook until softened, about 5 minutes. Reduce heat to low, cover, and cook until turkey parts and onion release their juices, about 15 minutes. Stir in broth, water, thyme, and parsley, bring to boil, and adjust heat to low. Simmer, uncovered, skimming any impurities that may rise to surface, until broth is rich and flavorful, about 30 minutes longer. Strain broth into large container and reserve giblets. When cool enough to handle, chop giblets. Refrigerate giblets and broth until ready to use. (Broth can be stored in refrigerator for up to 1 day.)

2. While turkey is roasting, return reserved turkey broth to simmer in saucepan. Melt butter in separate large saucepan over medium-low heat. Add flour and cook, whisking constantly (mixture will froth and then thin out again), until nutty brown and fragrant, 10 to 15 minutes. Vigorously whisk all but 1 cup of hot broth into flour mixture. Bring to boil, then continue to simmer, stirring occasionally, until gravy is lightly thickened and very flavorful, about 30 minutes longer. Set aside until turkey is done.

3. When turkey has been transferred to carving board to rest, spoon out and discard as much fat as possible from pan, leaving caramelized herbs and vegetables. Place pan over 2 burners set on medium-high heat. Return gravy to simmer. Add wine to pan of caramelized vegetables, scraping up any browned bits. Bring to boil and cook until reduced by half, about 5 minutes. Add remaining 1 cup turkey broth, bring to simmer, and cook for 15 minutes; strain pan juices into gravy, pressing as much juice as possible out of vegetables. Stir reserved giblets into gravy and return to boil. Season with salt and pepper to taste, and serve.

BREAD STUFFING WITH FRESH HERBS

Serves 10-12

Two pounds of chicken wings can be substituted for the turkey wings. If using chicken wings, separate them into 2 sections (it's not necessary to separate the tips) and poke each segment 4 or 5 times. Also, increase the amount of broth to 3 cups, reduce the amount of butter to 4 tablespoons, and cook the stuffing for only 60 minutes (the wings should register over 175 degrees at the end of cooking). Use the meat from the cooked wings to make salad or soup.

2 pounds (20 to 22 slices) hearty white sandwich bread, cut into 1/2-inch cubes (about 16 cups)
3 pounds turkey wings, divided at joints
2 teaspoons vegetable oil
6 tablespoons unsalted butter, plus extra for baking dish
1 large onion, chopped fine
3 celery ribs, chopped fine
2 teaspoons salt
2 tablespoons minced fresh thyme
2 tablespoons minced fresh sage
1 teaspoon pepper
2 1/2 cups low-sodium chicken broth
3 large eggs
3 tablespoons chopped fresh parsley

1. Adjust oven racks to upper-middle and lower-middle positions and heat oven to 250 degrees. Spread bread cubes in even layer on 2 rimmed baking sheets. Bake until edges have dried but centers are slightly moist (cubes should yield to pressure), 45 to 60 minutes, stirring several times during baking. (Bread can be toasted up to 1 day in advance.) Transfer to large bowl and increase oven temperature to 375 degrees.

2. Use tip of paring knife to poke 10 to 15 holes in each wing segment. Heat oil in 12-inch skillet over medium-high heat until it begins to shimmer. Add wings in single layer and cook until golden brown, 4 to 6 minutes. Flip wings and continue to cook until golden brown on second side, 4 to 6 minutes longer. Transfer wings to medium bowl and set aside.

3. Return skillet to medium-high heat and add butter. When foaming subsides, add onion, celery, and 1/2 teaspoon salt. Cook, stirring occasionally, until vegetables are softened but not browned, 7 to 9 minutes. Add thyme, sage, and pepper; cook until fragrant, about 30 seconds. Add 1 cup broth and bring to simmer, using wooden spoon to scrape browned bits from bottom of pan. Add vegetable mixture to bowl with dried bread and toss to combine.

4. Grease 13 by 9-inch baking dish with butter. In medium bowl, whisk eggs, remaining 11/2 cups broth, remaining 11/2 teaspoons salt, and any accumulated juices from wings until combined. Add egg/broth mixture and parsley to bread mixture and gently toss to combine; transfer to greased baking dish. Arrange wings on top of stuffing, cover tightly with aluminum foil, and place baking dish on rimmed baking sheet.

5. Bake on lower-middle rack until thickest part of wings registers 175 degrees on instant-read thermometer, 60 to 75 minutes. Remove foil and transfer wings to dinner plate to reserve for another use. Using fork, gently fluff stuffing. Let rest 5 minutes before serving.

CLASSIC MASHED POTATOES

Serves four

Russet potatoes make fluffier mashed potatoes, but Yukon Golds have an appealing buttery flavor and can be used.

2 pounds russet potatoes
8 tablespoons unsalted butter, melted
1 cup half-and-half, warmed
Salt and pepper

1. Place potatoes in large saucepan and cover with 1 inch cold water. Bring to boil over high heat, reduce heat to medium-low, and simmer until potatoes are just tender (paring knife can be slipped in and out of potatoes with little resistance), 20 to 30 minutes. Drain.

2. Set ricer or food mill over now-empty saucepan. Using potholder (to hold potatoes) and paring knife, peel skins from potatoes. Working in batches, cut peeled potatoes into large chunks and press or mill into saucepan.

3. Stir in butter until incorporated. Gently whisk in half-and-half, add 1 1/2 teaspoons salt, and season with pepper to taste. Serve.

Ever since writing has existed, people have wanted to send secret messages to one another--and others have wanted to intercept and read them. This is the second installment of a blog series taking you through the history of cryptography, its present, and future possibilities of unbreakable codes. Click here to read Part 1: Encryptions Past.

Some of the very first secret codes were substitution ciphers--schemes for transforming the letters in a message to render them unreadable to anybody who didn't know the secret to decoding them. The reader of the message would use a "key," information that revealed how to translate the message back into normal text, that could come in the form of an exact list of letters or numbers, a code word, or another variable. In theory, only people with knowledge of the key could read the encoded messages. In practice, though, the earliest ciphers were simple enough to break by analyzing the frequency of letters or simple trial and error.

The good news for secret-keepers: In World War II, an unbreakable encryption scheme was invented. The bad news: The One-Time Pad, as it was called, never really caught on. And for good reason.

Here's how it worked. Users would need two identical copies of a long book of random numbers--the "One-Time Pad" itself. The first message sent would use the first page of the One-Time Pad, and each subsequent message would use a new page, so that by the 999th message both communicators would have gone through 999 matching pages of random numbers.

Because the numbers in the key didn't repeat, there were no patterns to analyze: hence the unbreakableness. Sure, a spy could guess the exact string of random numbers used and decode the message. But how would he know it was the right message? With a slightly different string of random numbers, the message could decode to say something completely different, and there was no way to verify a correct decoding.

Unbreakable it may have been, but the One-Time Pad was also rather inconvenient. Bulky books of random numbers were impractical to carry and use on the battlefield. There was always the risk that they would be stolen by the enemy. Even the process of generating truly random numbers was much more difficult than you'd expect, and any patterns in the numbers could be exploited to crack the code. The unbreakable One-Time Pad points to the problem with all ciphers invented up to this point--in order to send a secret message, the sender and recipient had to already share a secret: the key, whether it was a list of letters and their counterparts or a book of random numbers. And the system would only be as secure as the method used to share the key. It would be quite some time before anybody overcame that particular hurdle.

German Enigma machine. Via Wikimedia.

So far I've only talked about pen-and-ink ciphers: the kind that are easy to encrypt and transmit by hand. But the push for more complexity meant, that during World War II, armies were always on the lookout for a fast, convenient way to send out orders and information. Pen and paper gave way to simple mechanical devices, which soon blossomed into complex machines whose codes required even more complicated machines to crack. A famous example: Germany's use of the mechanical encryption system called ENIGMA to conceal its plans. ENIGMA was powerful because it was flexible: the machine's settings allowed users to access a huge number of encryption schemes based on keys that were shared among all the operators and changed by the day.

Here is how the process worked: ENIGMA sent each typed letter through three of its many scrambling rotors. At each rotor, ENIGMA switched the letter with another letter. Then, the letter went through a plugboard that could swap several letters with each other--the swap list was changed every day. After every key type, the rotors would increment forward, ensuring that the encryption of the next letter would be different. The message could only be decoded if the machine was set up with the identical rotors in the same position and the same plugboard settings--leaving 159 million million million possible "keys" or settings for a given message's beginning. (See How the Enigma Works for more about ENIGMA's inner workings.)

Because the plugboard and rotor settings were changed by all ENIGMA users on a daily basis (each ENIGMA operator had a thick book of settings to use each month), British scientists were forced to rush and break the code each day to read transmissions before the information became obsolete.

The race to break ENIGMA is a famously dramatic story. Ultimately, the scientists at Britain's Bletchley Park invented a mechanical device the size of several rooms to crack the code. Their machine was built of several pieces called bombes that recreated ENIGMA's internal machinery. These bombes automatically cycled through trying all the possible rotor combinations to break the day's transmissions. The bombes were precursors to the computers we know today; ENIGMA motivated scientific development and showed the world the possibilities of using machines to encode and transmit information.

Today, you can use a computer to create a polyalphabetic substitution code complicated enough that it would take impossibly long for someone to decode without the key. And indeed, many encryption systems available commercially rely on that basic format.

But isn't there a way to get rid of this reliance on secret keys?

Well, yes--as we'll explore next.

NOVA scienceNOW's "Can Science Stop Crime" introduced you to Tadayoshi Kohno, a University of Washington computer scientist who's made it his mission to take over networked machines, identifying surprising security holes that the bad guys can make use of. But hacking isn't just a question of guessing a password--systems use a process of encryption to mask information, making it a meaningless jumble of code unless you possess a secret key.

Ever since writing has existed, people have wanted to send secret messages to one another--and others have wanted to intercept and read them. These days, the "messages" are bank information, government files, or control over surveillance systems. The eavesdroppers have evolved into hackers and government agencies like the NSA. But the constant power struggle between secret keepers and secret stealers continues apace, spurring new invention and broadening the horizons of science along the way. Over the next week, this four-part blog series will take you through the history of cryptography, its present, and future possibilities of unbreakable codes. 

Encryptions Past

LHIEL XEU SRWP R SLNVAB VX TNO VQ XDMZ SRV DLLH XMABADIU QVWVXDIE

Ever send a secret message to a friend to avoid the snooping eyes of a younger sibling? If so, you're probably already familiar with the sort of encoding techniques I'll describe here, the earliest examples of substitution ciphers: schemes for replacing letters with others to render a message unreadable.

The first recorded examples of ciphers--specific procedures for encrypting information--replaced each letter in a message with a different letter. ("A" would always be replaced by "S," for example.) Simple versions of these ciphers were supposedly first used by Julius Caesar to transmit battle commands, and they're even sometimes called Caesar ciphers.

This sort of cipher is monoalphabetic because it assigns just one specific code letter to each letter of the alphabet in the message. It comes with a key that specifies how to change each letter to disguise the message and how to reverse the change to read it. The key could look something like:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
L A Q E F J S W B H I M P G U T X R Z O K N C Y V D

Using this key, the code LOOK BEHIND YOU would translate to MUUI AFWBGE VUK.

Of course, as these ciphers entered wide use, people quickly began to discover ways to read the message without being given the key. Look at our example--the repeated UU in the first word could only be something like EE or OO, and trying different substitutions lets you work out the original message. The longer the message, the better letter frequency analysis will work.

Secret keepers were forced to up the complexity of their codes. The result was the polyalphabetic ciphers--a method which switched the encoding process of each letter throughout the message, so "A" might be replaced with "S" at one time and then with "R" later on in the message, all according to a set pattern. The more complicated the key, the harder the message would be to figure out. However, tools like frequency analysis could still crack secret messages when the text was long enough, because the key would have to repeat--meaning some parts of the message would be encoded with the same substitutions as others.

Armies and civilian secret-keepers alike quickly took up polyalphabetic ciphers as a much more secure way to communicate. To code them quickly, senders used tools like the cipher disk in the image below. This disk was standard issue for Confederate officers during the Civil War.

A reproduction of a Confederate cipher disk. Via Wikimedia.

This Confederate cipher wheel can implement a Vigenère Cipher, which uses a key phrase or sentence to encode a message. For each letter of the raw message, you'd turn the dial so "A" on the outer circle lined up with the letter in the code phrase on the inner circle. You'd then find the letter from your message on the inner circle and substitute the matching letter on the outer circle! Rinse and repeat for each letter of the code phrase and message.

This was the state of substitution cryptography before the advent of complex calculating machines. Soon, mechanical developments would make this sort of code look like child's play.

Our blog series on cryptography will continue later this week.

It was with great pleasure when on Tuesday morning I read that Serge Haroche and Dave Wineland had been awarded the 2012 Nobel Prize in Physics "for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems."

Quantum mechanics is the branch of physics that describes how matter and energy behave at the most fundamental scale. Everything is, at its most basic, quantum-mechanical. Atoms obey the laws of quantum mechanics, and so do soccer balls. So why wasn't famed Argentine soccer player Lionel Messi also part of the citation? After all, one of the key features of quantum mechanics is the ability of a single atom to be in several places at once, and Messi can manipulate a soccer ball to similar effect. That's because atoms behave in far stranger ways than soccer balls. Over the last few decades, Haroche and Wineland have measured and manipulated individual atoms in ways that are stranger and more stirring than any World Cup soccer match.

At the beginning of the twentieth century, founders of the then new discipline named it quantum theory, after the Latin word meaning, "how much". They used the word quantum to signify phenomena that one normally thinks of as continuous, such as waves of light or of sound, that are fundamentally discrete. Light, for example, is made up of elementary excitations called photons--particles of light. Similarly, sound is composed of particles called phonons. The motions of electrons in atoms are also quantized, resulting in a discrete set of possible energy states for atoms. When an atom moves from one such energy state to another, it absorbs and emits photons and phonons. In quantum mechanics, continuous things turn out to be discrete. Conversely, things that we think of as being discrete and chunky like atoms or, for that matter, soccer balls have a continuous, wave-like quality to them. This interplay between continuous and discrete natures is known as wave particle duality.

Quantum mechanics is famously weird--its predictions are strange and counter-intuitive. A single atom can be in two places at once. A measurement made on one particle can apparently instantaneously affect another particle light years away, an effect that Schrödinger called entanglement, but that Einstein termed "spooky action at a distance." The detailed dynamics of the interaction of atoms with light and sound is a complex quantum dance replete with all sorts of quantum weirdness. As atoms absorb and emit light, they are in two different energy states at once, and the emitted photons and phonons are entangled with the atoms and with each other. Haroche and Wineland are masters at controlling and directing this herd of elementary particles.

The atom wranglers

To see exactly how deep an impression Haroche and Wineland made on our field, let's take a trip to the American West, where I was living in the summer of 1994. There, a wrangler is a cowboy whose job it is to herd horses and cattle. Cattle on the range are ornery, and it requires lots of wrangling to convince a herd to go one way or another. That summer in Santa Fe, I wasn't wrangling cattle but herds of atoms to make them exchange photons and phonons with each other. I wanted them to perform a particular task. I wanted to make the atoms compute.

Computers operate by flipping bits, the smallest possible chunks of information. A bit represents the distinction between two possible states--yes or no, true or false, zero or one. Their quantum nature makes atoms, photons, and phonons digital; they naturally represent bits. For example, an atom in its lowest energy state or ground state can be taken to represent zero, while the same atom in its first excited energy state represents one. A polarized photon whose electric field wiggles back and forth horizontally can be taken to represent zero, while the same photon wiggling back and forth vertically represents one. The presence of a phonon can be taken to represent one, while its absence represents zero. A herd of atoms exchanging photons and phonons is basically a bunch of bits flipping back and forth. If you could wrangle that herd so that it flipped its bits in the right way, I reasoned, those flipping bits would constitute a computation.

In the 1980s, David Deutsch and Richard Feynman had come up with applications for such quantum computers, if they could only be built. In 1993, I had come up with a plan to make a herd of atoms compute. If you took that herd and zapped them with a carefully crafted string of pulses of laser light--a technique called electromagnetic resonance--then the natural interactions between the atoms would allow them to flip their bits in the form of a computation. In fact, their quantum nature would make them compute in a particularly weird way. As an atom emitted or absorbed a photon, it could be in both the ground state and the first excited state at the same time. The atoms quantum bit, or "qubit," would represent zero and one simultaneously. Interactions between atoms and light could create entanglement and spooky action at a distance.

My plan looked good on paper, as I'm sure did many a plan to take a herd of Texas cattle from Red River to Kansas along the Chisholm trail. But to put it into action, I needed a real atom wrangler, an experimentalist who could actually coax atoms and photons into doing what she or he wanted. Folks told me that the best atom wrangler around was Jeff Kimble of Caltech. So I made the trip from Santa Fe to Pasadena to meet with Jeff and his atoms.

Jeff Kimble is a tall Texan, well-known for having squeezed light harder than it had ever been squeezed before. After we shook hands, my fingers knew how that light felt. Along with Serge Haroche, Jeff is the world master at dripping atoms through optical cavities and having each atom interact strongly with an individual particle of light. Jeff looked at my plan, laughed because he knew it would be difficult to implement, and then got us down to the real business of making atoms and photons perform quantum logic. He also suggested that I head up to Colorado to talk with Dave Wineland.

For years, Dave Wineland and his group at the National Institute of Standards and Technology in Boulder had been building ion traps in order to make more accurate atomic clocks. But when he saw a proposal in 1995 by two brilliant theorists at the University of Innsbruck, Ignacio Cirac and Peter Zoller, he could make ions compute. Cirac and Zoller had come up with an alternative plan for building a quantum computer. Like my proposal, their method involved zapping atoms with lasers. In their case, however, the atoms were ions trapped by electromagnetic fields and interacting with each other by the exchange of phonons--quantized vibrations induced by the electromagnetic repulsion between the ions. Chris Monroe, a young scientist running Dave's ion trap, immediately set to work. Within just a few months, Chris and Dave had the first ion trap quantum computer up and running, performing simple quantum logic operations. When I visited them that year, they had that ion trap twisting and jumping with quanta and had lassoed ions and photons to perform all kinds of quantum weirdness.

The quantum cat's meow

Perhaps the funkiest quantum state that Wineland and his group produced was a so-called "Schrödinger's cat" state. Erwin Schrödinger, in his work of 1935 where he coined the notion of entanglement, suggested the following quantum thought experiment: Imagine an apparatus where the presence of an atom in one place triggers a sequence of events that kills a cat, while the presence of the atom in another leaves the cat alive. Now have the atom be here and there at the same time--completely allowed by the laws of quantum mechanics. The result is a cat that is simultaneously dead and alive.

In the Wild West, a sheriff tracking a bandit would put posters that read, "Wanted: dead or alive." If Schrödinger's cat had been the bandit, the bounty could have been double--it was both dead and alive at the same time. If there was any scientist who could make good on that bounty, it was Dave Wineland. In fact, with his wiry build and full moustache, Dave bears a striking resemblance to the legendary lawman Wyatt Earp. More peaceful than Earp, and kinder to animals than Schrödinger, Dave and his colleagues trained their lasers on an ion in their trap to construct a kind of "Schrödinger's kitten," a quantum of a state in which a whole herd of sound particles (phonons) is both over here (dead) and over there (alive) at the same time.

Meanwhile, in the decidedly non-wild western confines of the École normale supériure, the brilliant French scientist Serge Haroche was persuading herds of photons to be both here and there at the same time. Born in Morocco, Haroche's career was marked by a meteoric rise through France's grandes écoles. He was a true quantum wrangler--ever sensitive to the nuances and moods of the atoms--using his atom-optical Schrödinger's kittens to probe atoms' delicate relationships with their environment. The process by which a quantum system such as an atom flips between being here and there simultaneously to being here or there is called decoherence. The interaction between an atom and other atoms and photons in its surroundings causes that environment effectively to measure the position of the atom. Haroche noted that the highly non-classical quantum state of the Schrödinger's kitten caused it to be highly sensitive to decoherence.

Weird entangled states are often highly sensitive to decoherence--they lose their ability to be in two places simultaneously. This sensitivity makes quantum computation more challenging than ordinary digital computation, and that made Haroche skeptical about the possibilities of large-scale quantum computing. Interestingly, the same physics that makes some entangled states more sensitive to decoherence makes others completely insensitve. These insensitive states are the basis for quantum error correcting codes that allow quantum bits to be flipped in a way that is protected from environmental influences.

I first met Haroche at a conference in Santa Barbara in 1997, where he was declaring that sensitivity to the environment would prevent quantum computers from ever being constructed. I teased Haroche for being too much like Einstein, who had made great contributions to quantum mechanics without ever fully believing in it, a ribbing which today remains true: Haroche has made heroic contributions to the field of quantum computing without believing such computers can be built.

The quantum sensitivity Haroche identified certainly makes quantum computers hard to build, but it's also that very sensitivity that makes funky quantum phenomena such as Schrödinger's cat states the basis for hyper-sensitive detectors and measurement devices. Recently, Wineland's group and others around the world have used quantum interactions between light and atoms to produce optical-frequency atomic clocks that have the potential to be many orders of magnitude more precise than existing atomic clocks. What's bad for quantum computation is good for precision measurement--if life deals you quantum lemons, make quantum lemonade.

Back in the quantum saddle

By wrangling atoms and light, Wineland, Haroche, Kimble, and many others--Nobel laureates and not--have attained an intimacy with the quantum world as never before. These 'quantum whisperers' know how to coax atoms and photons down their weird paths because they know just how weird those paths are. You don't convince people to do things by quarreling with them. Yes, they can be moved by force, but in the end people, horses, soccer balls, and atoms attain great things only when treated with sensitivity and respect.

The 19 worst passwords, as identified by SplashData.

If your go-to password is "password" or "123456," you should probably stop reading and go change it--both topped SplashData's list of the most common passwords of 2011. The software company was able to create this list by analyzing millions of passwords that hackers had stolen and posted online. According to SplashData CEO Morgan Slain, "password" and "123456" were among the ten most common passwords in over 90% of the individual files hackers posted.

Microsoft researcher Cormac Herley, who specializes in computer security, said based on the lists of stolen passwords he has seen, he suspects that between 0.2 and 0.5 percent of all passwords are the word "password." If that's true, a hacker trying to break into 1,000 different accounts using "password" will likely gain access to between two and five of them.

If you didn't find your password in the above image, don't applaud yourself quite yet. Having a strong, hard-to-guess password can only do so much. "It's definitely better, but it's better against one particular type of attack," Herley said, referring to the "guessing attack" described above in which a hacker tries different username and password combinations to gain access to an account.

Unfortunately, hackers usually take more efficient routes. Sometimes they exploit weaknesses in applications within internet browsers to secretly install keystroke-logging software onto users' computers; other times they create seemingly-innocent websites that lure users to directly reveal their login information. "If you [inadvertently] install something that's a password stealer, it doesn't matter how strong your password is," Herley said.

To protect yourself from these types of attacks, Herley recommends that you run up-to-date software. Hackers often exploit known vulnerabilities in applications like Flash or Java, and the longer a version of a program has been available, the more likely it is that hackers have learned how to break into them. He also recommends installing antivirus software.

Hackers also target servers directly. In 2009, someone broke into the server of the social-gaming site RockYou and released over 32 million passwords, including user login information for partner sites like MySpace. Websites are supposed to encrypt passwords, meaning that rather than storing a user's actual password, they store a "hash"--the result of a specific function calculated on it. But RockYou had stored the passwords in plain text, meaning when hackers gained access to the database they found an easily exploitable list of usernames and corresponding passwords. Herley called this "really, really bad practice."

Although there is no foolproof way to protect yourself from an attack on a server, Herley said you should take measures to ensure that a breach on a low value site does not compromise their security on a more important one. Although creating new passwords for each site one uses is sound advice, in practice, people may not be able to choose unique passwords for every single account they have. Herley recommends that users rank them in order of importance--creating a unique password for one's email account is likely more important than making five different passwords for five different online magazine subscriptions.

Given the various ways in which hackers can exploit traditional password login systems, one may wonder why we still use them. Researchers have proposed and developed new ways of verifying an individual's online identity. Sites could require users to scan their fingerprints or insert personalized smart cards into specialized readers attached to their computers. But Herley said he doesn't see the new technologies replacing traditional login systems any time soon for one main reason: cost. No new technology, especially one that requires a physical device, will ever be cheaper than passwords, which essentially cost websites and users nothing.

He used Facebook's "explosive growth" as an example. The site grew to nearly one million users before it received any big investments, a feat that would have been impossible had authenticating the identity of each user cost even as little as ten cents.

Sites' continued reliance on traditional verification methods does not mean that internet security has stopped improving. Companies are constantly working behind the scenes to augment password systems, implementing new techniques of verifying user identity such as tracking the locations of the computers in which a user logs in. If a website detects something unusual--like a login on a new computer in a different country--it can boost its security by requiring the user to enter additional information, like a code that is text messaged to the number linked to the user's account.

As the methods sites use to protect users' information advance, so too will hackers' determination to crack them. But before you spiral into panic, rest assured that although a spammer might find his way into your Facebook or email accounts, most Internet users will never suffer from a devastating theft of cyber identity. Still, "Anyone who has been online for any amount of time should have their guard up," Herley said. He means you, "password" users.

A robot scuttles forward slowly, its motion driven by vibrations on three tiny legs. It executes one of the few simple programs housed in its microprocessor and circles randomly as it flashes an infrared light at the ground, searching. Every so often it flickers a colored LED. The robot's about the size of a quarter, so feeble that its forward progress can be stopped by a flat piece of paper, and so helpless that if it should fall it would be unable to get back up. All in all, the robot is rather unimpressive by itself. But then, Kilobots aren't meant to be considered on their own.

And this lonely Kilobot is searching for more of its kind. The robot's infrared detector picks up some light bounced off the ground by another bot, and it heads towards the source of the signal. Soon, identical robots surround it; as it spins it detects signals everywhere as other robots stream towards the group. The Kilobot's found the others: the 1,000-robot swarm. Now the real work can begin.

Radhika Nagpal's Self-Organizing Systems Research Group at Harvard is at the forefront of swarm robotics, and its thousand-robot army is almost complete. Swarms in nature--like those formed by colonies of ants, bees, or termites--fascinate scientists because, even though one individual in the swarm has only a small set of actions and works autonomously of all the others, somehow the actions all build up to produce very complex group behaviors.

Mike Rubenstein, a postdoc in the lab, describes an inspiration behind the pursuit of robot swarms: "Millions of termites will build mounds of dirt in Africa; towers that are meters tall. There's no leader, they're doing whatever they want to do, they're blind, they're a couple millimeters in size...yet somehow they're still capable of building these huge complicated structures to help them." Rubenstein and the others at the lab try to create collective behaviors from their own simple building blocks: in this case, tiny robots.

The Kilobots can move objects several times their weight, synchronize patterns of flashing lights, and map their immediate locations. Here are a few clips of smaller Kilobot swarms in action: pivoting, sensing one another, following the leader, and even foraging for "food."

Writing programs for swarm behavior is a popular computer science pastime, but most large-scale swarms only exist virtually. A real-life swarm of this magnitude will allow researchers to see how swarm programs work in realtime. Since the project was revealed in 2011, the lab has almost reached their goal of 1,024 robots, and they've already discovered that there are unique hurdles to be overcome where giant swarms are concerned.

Having that many robots creates a tricky set of challenges, explains Rubenstein. "Everything you do on the robots has to be done on a collective level, as a whole, and not on the individual," he says. "You can't have a power switch that you push on each robot. You can't have a programming cable that you plug into each robot. You can't have a charging cable that you plug into each robot...."

To address this, the team had to think creatively. Each Kilobot has a conductive spring on top and conductive legs, and they're charged en masse by running a current through them via metal plates placed above and below them. The team programs the entire swarm at once by beaming a stream of infrared flashes in their direction; the robots pick up the infrared light with specialized sensors. It takes 35 seconds to send a program to the robots, whether the swarm's just a few or all 1,000. The same overhead system is used to wake the robots out of sleep--a state in which they turn all circuitry off, but revive for 10 milliseconds every 8 seconds to check for a wake-up call. The Kilobots can last a month without charging in this state.

The other obvious problem is construction--how do you get to 1,000 robots? A single Kilobot is inexpensive at just $14 worth of parts, and only takes five minutes to assemble. That's "only" $14,000 and over 83 hours of construction to create the swarm members. In addition, the lab has made the Kilobot design available to other labs, so someday labs everywhere can test out their programs on huge generalizable swarms.

The Self-Organizing Systems Research Group is also trying out more single-purpose swarm robots: TERMES, for instance, are construction robots that take inspiration from nature's termites. The palm-sized robots, which also operate in swarms, move foam blocks to construct any inputted structure.

The cool thing about TERMES is that you can set any number of them on the task and expect a completed product. "They're capable of building guaranteed structures," says Rubenstein. "You start them off and you're guaranteed the structure will be built after a certain amount of time." They will finish it eventually even if the structure is destroyed halfway through, or if robots are added or taken away from the team. Somehow, with only the ability to see just a short distance in front of them, they'll manage to put it together every time.

See what I mean in the video below: TERMES hard at work climbing, grabbing, and building structures virtually and in real life.

What could the future hold for robot swarms? Robots that attach to each other--"like Legos or Transformers," according to Rubenstein--could combine to form large, adaptable robots suited for a variety of tasks. The lab is already working on modular robots that can move collectively and work together, like supporting a table perfectly level as the surface beneath it moves. Robots like TERMES could build structures in hard-to-reach places, from caves to outer space.

Another application, someday, could be smart matter: Rubenstein envisions something like "a bucket with millions of sand-like particles, each a small robot that could attach to its neighbors." With this, you could reach in and pull out any tool, just by letting the robots know how to connect to form the object. It would be just like "an infinite toolbox in a small bucket of sand."

Smart matter may be far in the future--the "nano" level robots--but the lab's Kilobots and TERMES show that swarms of mini robots are becoming a tangible reality. There's power in numbers, and who knows what Kilobots and their descendants will learn to do next.

This summer, we have mourned the loss of two great astronauts, Neil Armstrong and Sally Ride. I was born in 1990--too young by far to have witnessed the Apollo missions or even the early days of the shuttle era--and so for me, Armstrong and Ride have always been names in textbooks. Now I am reminded of how very human they, and the adventure of exploration on which they brought us all along, are.

Their lives remind us that science is a process founded on the enthusiasm of individuals, groups, and the public. We need individuals who can approach science the way Armstrong and Ride did--as an adventure, and an experience to be shared.

Yet for me--and, I suspect others of my generation as well--it sometimes feels like that adventure was over before we could ever join in; as if we'd just opened the book to find that what we'd hoped was the prologue was actually the final chapter.

Is this really the end of an era? Not at all. NASA's Curiosity rover landing just a few weeks ago sparked excitement all around the world not because it promised definitive, immediate answers on the habitability of Mars. It was exciting because it showed us that we are capable of more than we think. That was Neil Armstrong's attitude, and it's something every person--scientist or not--can hold onto.

On the other hand, last summer marked the end of NASA's decades-long space shuttle program. Unlike satellites and robotic rovers, the shuttle program literally sent people beyond our world. At the same time, it inspired people back home to try to break through their own boundaries.

As James Hansen, author of "First Man: The Life of Neil A. Armstrong," told CBS in a widely-quoted interview: "All of the attention that... the public put on stepping down that ladder onto the surface itself, Neil never could really understand why there was so much focus on that."

Maybe that's why Armstrong was so humble. It wasn't so much about stepping onto the moon as it was the thrill of his never-ending curiosity. Now I see him as a person who really enjoyed science for the way it propels us forward step by step--and not really in one giant leap.

The world watched in astonishment last week as NASA delivered its one-ton Curiosity rover to the surface of Mars with astonishing precision, hitting a target area just 12 x 4 miles wide after eight months and 352 million miles in space. While this epic engineering feat was unfolding, I was working on an upcoming NOVA show about another phenomenal achievement involving the precise tracking of objects in space--this one dating back more than 2,000 years. Unlikely as it might seem, a common thread of human ingenuity connects both endeavors.

The Antikythera Mechanism is an intricate ancient Greek astronomical calculating device that has only recently yielded up its secrets. In 1901 AD, a group of sponge divers accidentally discovered it while exploring an ancient shipwreck off the tiny Greek island of Antikythera. All that was left of the Mechanism was an inconspicuous lump of heavily corroded bronze that broke into fragments after it was taken to the National Archaeological Museum in Athens. Traces of carefully cut gearwheels were noted on these fragments, which eventually led to speculation that it was some kind of calculating device. But "decoding" the device has only been possible in the last decade, thanks to state-of-the-art x-ray imaging and digitally enhanced surface photography. In a program scheduled for air on November 21, NOVA presents the unique inside story of how an Anglo-Greek scientific team succeeded in piecing together the exact design and function of all but one of the Mechanism's 30 known bronze gearwheels. Their story is a tour-de-force of scientific detective work.

As reconstructed by the team, the Mechanism was a kind of miniature planetarium, using dials and pointers to show the positions in the sky of the sun, moon, and five major planets. But it was also a computer that predicted the future. By turning a hand crank, the user could read off the date, hour, and even the color of future lunar eclipses, which the Greeks regarded as divine omens. The Athenian navy suffered a calamitous defeat at Syracuse 413 BC when their general interpreted a lunar eclipse as a warning not to put to sea, leading them to be trapped in the harbor by the enemy fleet.

One of the first clues that the Mechanism had something to do with eclipses was when British mathematician Tony Freeth, one of the scientific team, reconstructed a large bronze gearwheel with 223 teeth. That number corresponds to a famous ancient astronomical cycle called the Saros, first recognized by Babylonian sky watchers centuries before the Greeks, and based on a pattern of lunar eclipses that repeats every 223 lunar months. If the eclipse connection seemed obvious, other aspects were baffling, such as an enigmatic pin-and-slot mechanism visible on one of four small gears attached to the big one.

After months of struggling with the problem, Freeth finally realized with a shock that the pin-and-slot mechanism exactly models the ancient Greek theory of the moon's motion, including extremely subtle variations in the moon's position in the sky. By the second century BC, ancient Greek astronomers had calculated these tiny variations with great accuracy, and now Freeth discovered that the Mechanism's engineer had managed to translate them into a complex geared mechanism of equal precision.

The implications are remarkable: the Antikythera Mechanism emerges as the world's first known computer, able to predict eclipses accurately for decades to come. It demonstrates its makers' passion for state-of-the-art astronomical theory and extreme mechanical ingenuity.

Of course, the ancient Greeks didn't get everything right. Since each tooth of the bronze gearwheels had to be cut by hand, the Mechanism's accuracy was limited, while the pattern of eclipses would eventually get out of synch with the Saros cycle. In addition, the Greeks understood the tiny variations they observed in moon's position differently than a modern astronomer. Today, we know these irregularities are due to the moon's complex elliptical orbit around the Earth, while the Greeks explained them with the help of combined circular motions, or "epicycles." It seems likely that the maker of the Mechanism visualized the sun, moon, and planets as revolving on concentric spheres around the fixed Earth.

Yet if that vision of the cosmos was limited, the Antikythera Mechanism is eloquent testimony to qualities the ancient craftsman shared with today's NASA engineers: a drive to impose order on the universe through exact mathematical prediction, reflected in elegant, highly precise, miniaturized design.

Too often, television shows mystify the achievements of ancient technologists by attributing the building of monuments like Stonehenge or the pyramids to lost civilizations or aliens. This denies ancient people their ingenuity and the thread of connection that links our minds to theirs, despite the gulf of thousands of years that separates us.

For more about the Antikythera Mechanism, see:

Edmunds, Mike G., and Freeth, T. 2011. "Using Computation to Decode the First Known Computer," IEEE Computer, July 2011, p. 32.

Freeth, Tony, 2009. "Decoding an Ancient Computer" in Scientific American, December 2009, p. 76.

Marchant, Jo, 2009. Decoding the Heavens, Da Capo Press.

"Ancient Computer" airs on PBS Wednesday, November 21 at 9PM/8C.

Now that the summer Olympics in London have come to a close, most assume performance-enhancing drug ("PED") testing has as well. However, PED laboratories test year round--during competition and off-season training--employing multiple technologies to keep athletes in check and sports drug free. To this end, tests are done routinely during the year to establish a baseline level for each subject, and to guarantee that all potential Olympians are tested at least once before competition.

In 2010, the last year for which there is officially published data, WADA--the World Anti-Doping Agency--executed testing on 180,584 urine and blood serum samples taken from athletes in Olympic sports alone (compared to 77,683 in non-Olympic sports). Peak sampling occurred in 2008, an Olympic year, with 202,067 individual tests. To handle that volume, WADA has accredited 35 established testing labs spread among 32 countries worldwide. These 35 facilities share the burden of proving whether an athlete has illegally enhance his or her performance using any of WADA's prohibited substances. In fact, every year the organization must update its banned-compound list to keep pace with contemporary use. Now, it is undeniable that performance-enhancing drug testing has evolved into a fully global pharmacology network.

Part of the impetus for such a vast net is the proliferation of prohibited substances use across multiple sports.

"We test for over 250 [prohibited] compounds," said Dr. Anthony Butch, director of the official WADA lab located at UCLA.

To illustrate the challenges of detecting one of so many illicit substances, Butch described the path of one subject's urine sample through his lab. In this example, he explained the processes involved in testing for testosterone and some 60 similar substances classified under anabolic agents on WADA's prohibited list. The complex procedure for one athlete's urine sample--from receiving, signing, unsealing, separating, testing and diagnosis--starts with the mail.

To begin, there is the knock on the door from the delivery service, he said, signaling samples have arrived.

"The first thing we look for is signs of leakage," Butch said. "Each box is sealed with tape, every athlete has A and B samples, and each vial inside has a cap or tape that must be broken once to get in."

Here begins the "chain of command," a sign-in process to document each stage in handling the vials. A laboratory employee signs for the package, another must sign when the seal is broken, and so on throughout every step. This is key because allegations of improper handling can affect the outcome of an athlete's appeal.

"All the appeals I've been to," Butch recounted, "[athletes] debate the chain of command. The science is pretty hard to argue."

After the urine samples are taken and logged, they are portioned into "aliquots," or, "little vials--about 20 for each A and B sample," said Butch. These 20 or so aliquots provide the amount needed for the many sub-categories (such as the 60-plus anabolic agents) of the prohibited substances to be detected. Aliquots are kept in a lock-and-key refrigerator until ready for centrifuge.

"Then, we look at color and pH," Butch described. "If [the urine] is clear, it's probably water. If it's purple, that's not urine. If the pH level is too close to 1.000, that's mostly water."

Following this are the gas and liquid chromatography phases, where individual compounds may be detected. This is a process of separating aliquots into their different components by exposing them to increasing gradients of high heat. First, Butch and his team pass small amounts of urine through a straw. "The garbage passes," he said, "and the steroids stick." Then, they wash the fine tube with solvents to concentrate samples.

The reason to use both gas and liquid chromatography in anabolic screening is because each of the more than 60 possible agents in that sub-category alone reacts uniquely to heat. In either gas or liquid state, the residues are placed in ultra-thin chambers with internal diameters of 0.25 mm wide and gradually subjected to heat in stages from 180 degrees Celsius, then to 230, to 270, and last to 300. At each level, a different compound will stick, then release.

"Those release times depend on the specific gravity [or, exact molecular mass]," Butch said. "We know from that if we have a positive sample."

For Dr. Butch, that's a standard urinalysis that he and his team can accurately complete within 48 hours. Accuracy is paramount, as testing stakes are incredibly high for athletes. One positive test could cause them to lose their Olympic eligibility, their medals, or face a suspension or ban from the sport.

"This is an Olympic athlete's career," said Dr. Butch, "You miss one 'Games' and you could be done."

Such precise testing is done in a place designed for such exacting work. Butch's officially certified WADA facility occupies 20,000 square feet just off the UCLA campus and employs 50 full-time medical professionals. In fact, it is the largest WADA-accredited PED lab on the globe. The United States is one of only three countries to feature two licensed centers. (The others are Germany and Portugal.)

"We test more than anyone else in the world," Butch said, "which is about 50,000 urine samples a year, versus 19,000 in the next highest lab."

That second-busiest processing facility for PED testing is in Salt Lake City, Utah. Dr. Daniel Eichner, a self-described friend of and collaborator with Butch, has run the Salt Lake facility for more than a year, having worked previously for both the Australian and U.S. Anti-Doping Agencies. Eichner said the importance to WADA of operating the second lab in the U.S. is for redundancy, "in the case the L.A. lab couldn't operate," he said.

Often, that lab must work on tight deadlines, such as during competition, Butch said. While industry standard turnaround for samples is 10 business days, during the Olympics it can shorten to 48-to-72 hours from receipt, through full testing, to return. Protocol demands that every Olympian be tested prior to competing, and be subject to random testing; some athletes undergo multiple tests. And, Olympic competition itself cues testing.

"Obviously, we must test the winners," Butch added. He said all medalists undergo testing immediately following their event.

Another lab imperative is when an "A" sample--which supplies the first round of testing--shows positive. Butch and his colleagues must then enact a round of testing for confirmation on the subject's "B" sample, which is the second of the required two batches collected from each subject. This second round is the same scientific process as the first, with added rigor and safeguards: all B samples, unlike A samples, are tested in isolated batches by a single technician so the sample never changes hands.

"A negative [untainted] test is my friend," Butch said. "It takes a lot of work to run the first test, let alone a second."

To advance his urinalysis science, Eichner's drug lab has concentrated on developing tests to identify new substances coming from the renegade black market. He is now focusing on blood analysis. Though serum must be kept cold (which is highly expensive and time-sensitive), popular human growth hormone is best detected through blood tests.

But, the importance of screening is not just to protect fairness in sport or to ensure the health of athletes, said Leslie Henderson, professor of physiology and neurobiology at the Geisel School of Medicine at Dartmouth College. She works with hamsters, mice and rats to detect the sometimes-permanent alternations anabolic steroids can inflict on the nervous system when taken during adolescence. Particularly shocking is her research with animal subjects, which has shown that steroid use during this life stage has lifelong effects including emotional hardships (depression, aggression, and sexual dysfunction), and physical ailments (like cancers and liver and kidney diseases). She hesitates to extrapolate too far, but has worried that these frightening results may prove true among people.

In the Olympic realm, Henderson mentioned, this would apply to young athletes, often teenaged women, in sports like swimming and gymnastics, where androgenic (male characteristic producing) drugs boost muscle mass, strength, and performance.

She hopes that her rodent research, drug detection by labs, and WADA regulation might inform and protect a coming generation of young athletes who may not understand the risk.

"Kids see these athletes with perfect bodies," Henderson. "They think they're healthy, but they're not."

Want to test your knowledge of performance-enhancing drugs? Take WADA's Play True Quiz.

"Touchdown confirmed." The room erupted with cheers, back-slaps, high-fives, hugs and tears. And that was just among us media representatives, tightly packed into the von Karman auditorium at JPL last night. But our joy couldn't compare to the raw emotion captured on the faces of the Mars Science Laboratory team members in mission control, via live feed. They had chalked up the years of hard work, and put reputations and careers on the line to make history. Curiosity, the most complex robotic rover every built, touched down on Mars in one of the most ingenious (some said "crazy") landing systems ever devised. We were the lucky witnesses and chroniclers of this amazing feat.

Throughout the evening leading up to the landing, members of the MSL team endured the scrutiny of our cameras with the amazing grace of Olympic athletes about to sprint for the gold. Except that for these engineers and scientists, there would be no equivalent of a silver or bronze medal. Only a safe landing for Curiosity would do--or game over. Less than three hours before landing, Tom Rivellini, veteran of several Mars missions and a specialist in landing systems, was the picture of calm. "I can't think of anything we should have done differently. If we'd had more time before launch, I'm not sure what we would have done with it." Then he made a wry grin. "Of course, Mars can always surprise us." Jim Montgomery, an engineer on MSL's radar system, was nearly vibrating with excitement. It was his first Mars mission and, he said, "I'm going to savor every minute of this night, and remember it forever. I'm confident we've done our job and the systems will work."

We caught Adam Steltzner on the JPL Plaza, just as dusk was falling. Lead engineer on MSL's Entry Descent and Landing (EDL) system, Steltzner is a master of the bon mot--so he surprised us when our camera rolled and his eyes welled up with tears, "Tonight my job on this mission is over. I've been involved with an incredible group of people, and now our work is done. The fates will decide."

If the fates were involved last night, they were exceedingly generous. Now two working rovers call the red planet home (Mars Exploration Rover Opportunity remains operational), and three satellites glint in its orbit. The US has had a continuous presence at Mars since 1997, a monumental achievement--yet we still have so much to learn from the red planet. As Mission Scientist John Grotzinger wrote in an essay published in the New York Times, Curiosity is not just a rover, it's a time machine.

Curiosity landed in Gale Crater; in its center, Mount Sharp rises some three miles high. This mountain preserves a record of Mars' history, in layers of rock that Curiosity is equipped to read like chapters in a book. The earliest chapters will take us back three billion years or more, to a time when Mars may have been like a twin of the early Earth--wetter, warmer, with a protective magnetic field and atmosphere. On Earth, traces of that distant time, probably not long after life arose, have been largely erased by tectonic processes. Which means Curiosity may uncover volumes not just about the transformation of Mars into a cold and arid planet, but also about the history of our own planet.

Today, NASA released a stunning photograph taken by the Mars Reconnaissance Orbiter: suspended from its parachute, MSL plunges toward the surface of Mars. Not only did we land on Mars last night, we also watched our own arrival.

Image credit: NASA/JPL-Caltech/Univ. of Arizona

This reminded me of our interview with planetary geologist Nathalie Cabrol. She believes that exploration is a survival instinct that goes back to the very earliest forms of life. "If a species stays in one place, it is susceptible to any change that comes along. But if it spreads to many environments, some individuals may die, but many more will adapt. The need to explore is there from the start." Cabrol contends that what we call "curiosity" came much later in evolution--when our species became self-aware and gave a name to that spirit of exploration. Last night we followed our curiosity all the way to another planet and looked back at ourselves. The view in both directions was glorious.