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.

Can't get enough of Curiosity? Neither can we. In this video, get a sneak peek at "Ultimate Mars Challenge," NOVA's upcoming look inside the Curiosity mission, as MSL Chief Engineer Rob Manning describes the feats of engineering required to land the Mars rover safely.

Whoever said scientists and engineers are not emotional? Tonight gives lie to that old canard. Jubilation, tears, and hugs burst out in the control room at JPL as Curiosity landed successfully. It was a wonderful thing to behold, because no one deserves success more than this hard-working and dedicated group from JPL, responsible for sending a rover the size of a car to Mars.

Everything appeared to go flawlessly. We've been hearing for months how risky the new landing system was, how we might not hear anything for several hours, how images would be long in coming. But when it happened, it was smooth as silk. Everything right on schedule. No moments of terror, let alone seven minutes of terror. And the images came right away, including the shadow of the rover on Mars.

These engineers made it look easy. They showed us that the best way to deal with the terrifying possibility of failure is meticulous preparation, testing and retesting, bringing a lot of great minds together. Mars is a dangerous place. It has killed many of our space vehicles. It tests us every time. This landing tonight shows we still have the right stuff. Let's hope we use it, to plan and execute future missions. A great nation explores.

Tonight is just the beginning. The best is yet to come. Pictures of Mars from Gale Crater, images as Curiosity heads for a mountain that rivals Earth's tallest peaks. Information will flood in from Curiosity the field geologist and geochemist. Perhaps we will learn if the molecules we associate with life here ever existed on Mars. And then we will begin to sort out if we really are alone or if life once existed elsewhere.

A great evening. Curiosity is safely on the surface of Mars. Good night, Curiosity. Get some rest. You have a lot of work to do.

Can you imagine what it must be like to be part of the Mars Science Laboratory team here at the Jet Propulsion Laboratory? Thousands of scientists and engineers have invested years in the success of this mission in the interest of advancing our knowledge about Mars. We know from past missions that at least in the past, Mars has had two of the three conditions essential for life: running water and a source of energy. Curiosity could tell us if it ever had the third condition: organic molecules, those long carbon chains that all life as we know it has. Not only will we perhaps learn if Mars has ever had life, we could also learn what happened to it. After all, Mars and our own planet Earth were once on a similar trajectory. But somewhere around 3.5 billion years ago, we can speculate that something on Mars went terribly wrong. As a result, the Mars we see now is terribly inhospitable to life, whereas earth is teeming with it.

Being able to answer these questions, learning about Mars and about Earth, finding out more about the conditions essential to life--all that is at stake. It hinges on the success of tonight's landing, in a little less than an hour from now. But there's much more at stake--the future of continued space exploration and the role it plays in planetary science. A failure tonight could put an end for many years to an already faltering space program. NASA has no large follow-on rovers to Mars planned. MSL is it. Perhaps a success, a perfect landing followed by lots of captivating science, will encourage more planetary missions, more robotic exploration, and perhaps even, someday, a manned mission to Mars.

And no one would deserve it more than the engineers and scientists responsible for this ambitious and risky MSL program. No one could blame them if they had a knot the size of Mars itself in the pit of their collective stomachs. But instead of nerves and jitters, there seems to be a strange calm pervading this group. They've tested and retested and everything seems to be on track. Mike Watkins, MSL's manager of navigation and mission design, just told us things have been looking so good, they didn't even have to make any last minute adjustments in trajectory. And Rob Manning, flight system chief engineer, said he's calmer than he's ever been on this program. The engineers have done all they can, and now it's up to the laws of nature, riding on the back of an amazing group of people's hard work and dedication.

And, of course, for them it will be a long night. The landing is just step one. Then they will be struggling mightily to get some pictures--to get Curiosity to begin to satisfy our own curiosity about Mars.

I arrived at JPL around 6 pm tonight and already the parking lot was filling up with press. There's true suspense here. Will Curiosity land safely on Mars? When I was here years ago for the landing of Spirit, it seemed a forgone conclusion that the landing would go as planned. If the engineer had doubts, they kept them to themselves. But with this mission, there's a frank acknowledgement of the risk. MSL is huge and its landing system is brand new. And more than this one mission is at stake. As one NASA public information officer told me, the whole future of the planetary program hinges on success tonight.

Standing beside a model of the Curiosity rover.

Now, the die is cast. This morning Earth time the engineers at JPL spoke to MSL and sent their last message before landing. No earthling will speak to it again until it's on the surface of Mars. Throughout MSL's long journey, according to Nagin Cox, part of the mission's operations team, they send commands to the rover three times a week. Mainly what they get back is telemetry--power, attitude, velocity, etc.

So what did they say this morning? Did they send last minute instructions? "Don't talk to strangers!" "Get plenty of sleep!" "We love you no matter how things turn out. We know you did your best." Most of all, "If you meet any Martians, send pictures!"

No, none of these sweet parental admonitions. Simply they told it to change its timer so it won't expect another call from Earth for 93 hours. As Nagin Cox explained, if MSL expects a message and it doesn't come, it might think there's something wrong with its mechanisms for receiving the message. It might start fiddling with things, changing settings, adjusting antennas. And that could mess things up. We don't want MSL doubting itself at the last minute!

Once Curiosity is safely on the Martian surface, hopefully, communication will resume. They'll command the rover every day. The scientists and engineers will all shift over to Mars time. Already, Nagin is wearing two matches--one for Earth time, the other for Mars. But its not really necessary. There's even an app for that!

Nagin's watch collection--two for Mars, one for Earth.

For nearly forty years, NOVA has been bringing viewers stories of exploration: From Mount Everest to Antarctica, from undersea volcanic ridges to toxic caves teeming with exotic life. But there is one destination we come back to again and again, always with something new to discover: Mars.

Why does Mars hold such fascination? It is Earth's twin gone wrong, so similar and yet so different. Mars shows us what Earth might have been; it is our cautionary tale, our there but for the grace of God planet. How did Earth get so lucky? Why is our planet lush with life while Mars is dry and desolate? Figuring out how and why our fates diverged is one of the great mysteries driving the exploration of Mars.

In the last decade, NOVA has "gone to Mars" three times, as we followed the scientists and engineers on the Spirit, Opportunity, and Phoenix teams. We were privileged to film them as they prepared, launched, and ultimately reaped the incredible scientific fruits of their audacious missions. This year, we're getting ready to visit Mars again as we follow the Curiosity rover now en route to Mars. Our film, which will premiere in November, will document what it takes to get Curiosity safely from Earth to Mars. The journey will be more complicated and riskier than ever before, as Curiosity is counting on an ambitious new sky crane landing system to lower it safely to the Martian surface. And unlike Spirit and Opportunity, the near-identical twin rovers, with Curiosity, we'll only get once chance to get it right.

Before Spirit touched down on Mars in 2004, principal investigator Steve Squyres reminded our crew that, at that time, two-thirds of all spacecraft that had ever gone to Mars had "died"--failed or crash-landed before they could do any science. Though the rover teams may consider it bad luck to speak this aloud, I saw it written on their faces the night that Spirit was set to land. It was one of the most thrilling nights of my professional life: Producer Mark Davis and I were camped out in the parking lot of the Jet Propulsion Laboratory. We'd rented a truck so that we could edit the last three minutes of our show--the three minutes in which viewers would find out if Spirit made it or not--in time for our broadcast just two days later. No outside members of the media were allowed into the control room, but we had a direct feed so that we could see and hear everything as it happened.

I remember clearly that terrible pause when Spirit was supposed to be landing but there was no communication, so there was no way to know if the rover was safe or not. In the control room, the scientists and engineers all held their hands to their chests, literally holding their breath as they waited for Spirit to send the signal that it had landed safely. And when that signal came, the utter joy on their faces!

These incredible scientists and engineers--men and women who chose to devote themselves to this extraordinary project; who, in a split second, could have lost a decade's worth of work--are the heroes of our films about Mars. Through television, millions of Americans been able to share the exhilaration we all felt that night and to see the incredible ingenuity, resolve, and teamwork that go into a mission to Mars. As a filmmaker, moments like these are precious: They are the moments when we go beyond just informing our audience and have the opportunity to truly inspire them.

I remember that after the show premiered, one viewer wrote into say that it was "the most exciting hour of TV I have ever watched." What a wonderful compliment! But I know that the excitement wasn't created by our producers; it wasn't manufactured in the edit room. It was all thanks to the scientists and engineers who poured their talent and passion into making the dream of exploration a reality.

That evening at JPL, I knew that we would be making many more films about Mars. But today, I wonder: Are we writing the final chapter in a story that has captivated the planet? It seems that exploration is being squeezed out of the tightened federal budget. When will we land on Mars again? The answer isn't clear.

Yet I believe that it is part of our destiny to explore and learn more about other worlds. In doing so, we learn more about our home planet--and about ourselves. We reap the benefits of technical spinoffs like flexible body armor and panoramic digital photography, as well as a host of intangible rewards: inspiring a new generation to pursue science and engineering careers; endowing them with a sense of wonder about our universe and our place in it; and giving them a glimpse of humanity at its very best, united around a common and peaceful goal.

True to its name, Curiosity travels to Mars with a heavy payload of questions. Some of these questions will be answered, but others will surely lead to new and even more exciting questions. It is therefore my deep and sincere hope that Curiosity will not be an end but the beginning of a new chapter in the story of Mars exploration.

Written with Kate Becker.

For the past eight years, I've been the Deputy Project Scientist on the Mars Science Laboratory mission, with its rover, Curiosity. It's the most ambitious robotic mission ever undertaken by NASA, with scientific goals to match. We're doing no less than delivering a state-of-the-art analytical chemistry laboratory to the surface of Mars, driving it up a three-mile-high stack of layered sediments, and attempting to determine whether our neighbor planet ever offered conditions suitable for life.

Watch members of the Mars Science Laboratory team explain the challenge of landing Curiosity on Mars in this video from NASA's Jet Propulsion Laboratory.

Beginning with a one-page list of mission objectives from NASA, thousands of engineers and scientists conceived a mobile robot geochemist, the size and weight of a small car, to be our virtual presence at Gale Crater on Mars. It was designed to be able to safely access more of Mars's surface (allowing the landing site to be chosen for science, not only for safety), live longer, drive farther, and do more than any previous Mars rover. It launched on the biggest rocket available, cruises to Mars in a capsule larger than Apollo's, and flies itself to its landing site, landing on its own wheels on Martian soil. Over 400 scientists around the world are now eagerly waiting its safe arrival on Mars this Sunday night, so we can begin our search for habitable environments within Gale Crater.

Last Thursday, the team of engineers and scientists who designed, built, tested, and operate Curiosity were summoned to the biggest auditorium we have on the campus of the Jet Propulsion Laboratory for a final "all hands" meeting before landing. These meetings are rare--only a few times has the whole team been in a room together in the past eight years. I expected a pep talk--you know, only a week until landing, look how far we've come, etc. But instead we heard a rather profound statement from one of our leaders: After next Sunday, your life will be different. Whether Curiosity lands successfully or not, we all will arrive at a different place in our lives on Monday morning, and everything we've experienced up to this point, the success, the challenges, the nervous excitement, the camaraderie, will be a memory that will fade with time.

I truly hadn't thought about this. Especially as a scientist on the mission, I've been focused mostly on what happens after landing, unlike the many engineers charged with building and testing the rover, or ensuring its safe cruise to Mars and landing. Those engineers will have finished their duties on Sunday, and will join the hundreds of engineers who have already moved on to other projects. But my life will change, too. The years I have spent in conference rooms sweating over details with the engineers, the joy I've had in explaining Curiosity's "terrifying" landing system and thrilling scientific mission (we're climbing a mountain!) with dozens of public audiences, the trials, heartache, and pride in our team's journey to this point, those chapters all will close on Sunday. It made me realize how much my life has become intertwined with this mission and with these people. When all goes well on Sunday, we'll celebrate like crazy, but then that eight years of our journey together will be complete. Life indeed will be different.

I think I feel compelled to write this because I'm one of the people who will continue, even for years, actually! My scientific colleagues and I will tell the world of our discoveries, write papers, and generally take a lot of credit for what happens on Mars. But while I'm still on this side of the landing, I can't shake the fact that I'm the recipient of the talent and passion of over 3,000 engineers who have put their lives into this rover. The scientists will get the keys to the car on Sunday, but we sure didn't build it.

As we said at the launch, and will say one more time on Sunday: Go MSL, and Go Curiosity!