Which is more dangerous: A shark or an asteroid? If the magical Risk Fairy fluttered over with her sparkly wand and offered you a chance to cancel out one of these two risks, which would you choose?

Let's run the numbers. In any given year, sharks kill about half a dozen people. Last year, the tally of asteroid-related deaths was zero. The year before that, it was also zero, as it was the year before that, and the one before that--and so on. In fact, the total number of human beings who have definitively fallen victim to asteroid strikes in all of recorded history is, you guessed it, zero.

But before you sic the Risk Fairy on those bloodthirsty sharks, consider this: If a killer asteroid were to strike the Earth, it wouldn't just pick off a couple of luckless surfers. An asteroid with a diameter of 5 km could kill a billion people. Not to get all 2012, but it could mean the end of civilization as we know it.

Searching for exoplanets is like trying to spot the Invisible Man: Since you can't actually see him, you have to look for clues he's left in the spaces he passes through. Astronomers have gotten pretty good at this: With nothing but shadows and gravitational traces to go on, they've picked out more than 450 planets beyond our solar system.

Now astronomers are targeting an even slipperier quarry: all-but-undetectable Earth-sized planets orbiting near the Jupiter-sized ones they've already fingered. They've found the Invisible Man; now they're looking for his invisible dog.

The anthrax case is closed. Or is it?

"It's like death by a thousand cuts," Hatfill, who is now 56, says today. "There's a sheer feeling of hopelessness. You can't fight back. You have to just sit there and take it, day after day, the constant drip-drip-drip of innuendo, a punching bag for the government and the press."

Science got investigators pretty far: It led them to one flask, in one lab, led by one scientist. But it didn't erase doubts from those who think that the Justice Department never really got their man.

It's seven months since I last blogged about Hubble

Less than five weeks after my last post (from the September press conference announcing the results of the mission), our film was broadcast and my work on the project drew to a close.

For scientists and humans everywhere who want to see what's out there, it has been the beginning of a new age, driven by a reborn Hubble that's many times more powerful than it ever was before. In just a few months of operation, the rejuvenated telescope has set new records in long-distance observations. 

And since distance equals time in astronomy, Hubble seeing farther away into space means we're also seeing closer to the beginning of the universe.  Hubble has now captured images of the earliest and most distant galaxies ever seen, groups of stars that were burning 600 to 800 million years after the Big Bang.

For astronomers who study the history of the universe, this early period is considered the dark ages, a time that we know little about - but Hubble is beginning to change that.  The telescope is revealing some of the earliest galaxies to form after the Big Bang, and scientists are finding them quite different from what they're used to seeing.  These baby galaxies are smaller, and shaped differently; rather than ellipticals and spirals, they appear irregular and disheveled. Their light is also bluer -- consistent with what would be expected from the earliest stars ever born.

Much of these revelations are a result of stunning imagery coming back from the Wide Field Camera 3 - the very camera that almost never got installed because of a stuck bolt on spacewalk #1.  

That fact alone reminds me in a vivid way how all this exciting science about the dawn of the universe would not be happening if it weren't for those seven astronauts who went to Hubble, and especially the four spacewalkers who actually had their hands on the telescope.  All the grand scientific theory that will come from the new Hubble is rooted in the ability of a guy with his hands on a wrench to free a stuck bolt.

One of the great things about my job as a Producer for "The Secret Life of Scientists" is that I spend a lot of time with people who are almost always wrong. Here's a sampling:

"So often in the lab I look at my cells, and they're not behaving, and there's so many things that are going wrong. I get so frustrated, and I think 'Why am I doing this?'"

--Eva Vertes, Cancer Researcher

"There's a frustrating, frightening feeling when you can't figure out what's going wrong--even though the experiment has failed again and again and again."

--Nate Ball, Mechanical Engineer/Inventor

"In science, you're wrong over and over again. Then you have a moment of clarity--then you're wrong again!"

--Allan Adams, MIT Physicist

And these are the smart kids?

Who sells seashells by the seashore? And, more importantly, why should you care?

Journalist Shelley Emling's got the answer to both of these questions in her recent book, The Fossil Hunter: Dinosaurs, Evolution, and the Woman Whose Discoveries Changed the World. She is Mary Anning and this pithy tongue-twister does no justice to her fascinating life as the world's first female paleontologist.

As for me, I had never heard of Mary Anning until just a few months ago when I caught an interview of Emling on the radio. She was discussing her biography of Anning along with another writer, Tracy Chevalier who had also recently published a novel inspired by Anning's life called Remarkable Creatures.

This year's Earth Day committee (whose members run the gamut from Shaquille O'Neal to Former Vice President Al Gore) is urging everyone to commit "Acts of Green" in observation of the 40th anniversary of the holiday.

Acts of Green are pledges to do something to celebrate the Earth--it could be as simple as taking some time today to head out into a park and appreciate nature, or turning out the lights and holding your own personal "Earth Hour."

It's great to see some of the ideas and pledges people keep sending in.

(Click on the image see a live version of the Acts of Green, and add your own ideas. You might have to reload a few times because of heavy traffic to the EarthDay.org site.)

It's been more than a year since I did my last formal exercise in energy conservation--the Powering Down blog right here on NOVA Online. But some of the habits I picked up then have stayed with me.

I still bike everywhere I go, and I still cover my windows in plastic during the winter months. (I was surprisingly excited to weatherstrip all my windows last fall. Apparently I'm a secret home-improvement geek.) I'm still vegetarian, and I'm  working on that whole "local, in season produce" thing. I turn out the lights when I can, and don't leave my computer on overnight. 

Earth Day has sparked so many more great ideas that I'm eager to add to my routine, like not requesting a receipt at ATMs, or using online banking to reduce the amount of mail that your financial institution sends out.

Add your Acts of Green. What ideas do you have?

With the 20th anniversary of the launching of the Hubble Space Telescope coming up this Saturday, April 24th, we thought it was worth noting, for all those Hubble enthusiasts out there, the various Hubble-related programs and web features we've created in recent years.


Hubble image of the Eagle Nebula, aka the Pillars of Creation, Courtesy Jeff Hester

Last August, we aired a segment on NOVA scienceNOW about the repair mission of May 2009. This fix, the final one Hubble will get, followed on four others -- in 12/93, 2/97, 12/99, and 2/02, respectively. We found the story of the 2009 repair such rich drama that we aired a full one-hour NOVA on it, Hubble's Amazing Rescue, in October.

The director of both programs, Rush DeNooyer, wrote a series of behind-the-scenes blog posts about the 2009 repair. He began on launch day, May 11, and last posted on September 9, when the first images from the new, improved Hubble came through. (They were stunning.) Watch for a new blog post from Rush this Saturday, on the anniversary.

Its name doesn't exactly roll off the tongue: ununseptium (oon-oon-SEP-tee-um). But like many things in science, what it loses in pizzazz it gains in accuracy. In Latin, ununseptium means "117," and it refers in this case to a new element scientists have just added to the Periodic Table.

I was in touch yesterday with Ken Moody, one of the scientists involved in the find. Ken is a research chemist at Lawrence Livermore National Laboratory; his collaborators on this project come from two U.S. universities, the Oak Ridge National Laboratory, and the Joint Institute for Nuclear Research in Dubna, Russia. Altogether Ken has helped uncover six new chemical elements, numbers 113 through 118.

I asked Ken, whose group's discovery of element 114 (ununquadium) we chronicled in a 2006 NOVA scienceNOW video segment, what it felt like when he and his team "saw" that first atom of 117. He said they weren't sure at first and so remained cautious.

"Sorry, no shouts of 'Eureka!', no joyous dancing in the halls, and no victorious toasting," Ken told me in an email. But a few weeks later the team detected a second tell-tale occurrence. "It was consistent with the previous event in most particulars," Ken wrote, "and while random events can always bite you when you have only one of something, if you have two and they look alike, the assignment is pretty definite." In the end, the team detected six atoms of the stuff, enough to secure ununseptium a place on the Periodic Table.

Hollywood couldn't have scripted a more perfect scene: A nine-year-old boy, tagging along on his father's archeological expedition to Cradle of Humankind, South Africa, is chasing his dog through the grass one morning when he literally stumbles across some fossilized bones. But these aren't any ho-hum, add-them-to-the-pile bones: They represent an entirely new hominid species, almost two million years old, which walked upright like modern humans but still had apelike arms for climbing trees. 

Last summer, when NOVA scienceNOW ran a segment on LCROSS (the "Moon Smasher" spacecraft) and its search for lunar water, the LCROSS scientists didn't know what they might find: All the evidence from Apollo suggested that the moon was a bone-dry wasteland. But in a matter of months, that picture changed dramatically.

In September, scientists announced that three spacecraft had independently detected traces of water ice speckling the lunar surface. LCROSS added its assent in November, when its science team announced that the little spacecraft's crash landing had blasted about twenty-four gallons worth of water-ice out of a crater near the moon's south pole.

And now, things are getting even wetter: Sheets of ice, up to 10 feet thick, may be coating the depths of shadowed craters near the Moon's north pole. The total haul: at least 600 million tons of ice.

That's the word from the Indian Chandrayaan 1 spacecraft, one of the trio of probes that made the first discovery of lunar water. Chandrayaan measured the ice using its onboard radar. The science team's best guess is that the ice was dumped on the moon by asteroid or comet impacts. Because the north-pole craters don't get any sunlight, the ice would stick around indefinitely.

What do PBS's premier science program and the ChickFight women's wrestling tournament have in common? Before last week, probably very little. But on Friday, a green-haired goth wrestler named MsChif swept into our production studio to be interviewed for NOVA's Web series "The Secret Life of Scientists."

In my 20 years at NOVA, I've met many interesting scientists--intrepid oceanographers, Nobel prize-winning physicists, my childhood idols Jane Goodall and Carl Sagan. Never, though, had I encountered a professional wrestler / microbiologist like Rachel, whose ring name "MsChif" only hints at the stunts she pulls during matches. (In one infamous brawl with a 270-pound wrestler known as "Amazing Kong," MsChif disqualified herself by spitting an "illegal" green mist at her nemesis.)