Can Extremophiles Survive on Europa?

A team of astrobiologists from Argentina have recreated the conditions of Jupiter moon Europa, to see if extremophile bacteria could survive the unwelcoming conditions of the Jovian system.

Interplanetary space is generally considered lethal to organisms thanks to high levels of radiation, intense vacuum conditions and extreme temperatures. But the team, lead by Ximena Abrevaya at the University of Buenos Aires, wanted to see if any hardy critters could tough it out.

Finding a likely candidate would certainly help recent research at the National Autonomous University of Mexico, where researchers used a computer simulation to find if life could spread into space, hitchhiking on space-faring rocks.

That team found that particles ejected from the Earth could reach as far as Jupiter and one of its 64 moons, Europa, which astronomers reckon has a huge salt water ocean underneath its icy crust. A good breeding ground for life. But could anything survive the trip?

The team from Buenos Aires created a vacuum with conditions similar to those which exist on the surface of Europa. They then placed three organisms in it: the hypersaline-tolerent Natrialba magadii, the salt-obsessed Haloferax volcanii and the ultra-hardy, all-around survivor Deinococcus radiodurans.

The researchers then blasted these critters with ultraviolet radiation at levels that might occur on Europa. After three hours of extensive radiation, the results came back: none of the H. volcanii survived, but small numbers of D. radiodurans and N. magadii could tough out the toxic rays.

D. radiodurans are well-known survivors, often called the world's toughest bacteria for their ability to shrug off extremely low temperatures, a complete lack of water, deadly vacuums and acid. In a past experiment using simulated Martian soil, 30 percent of a community of D. radiodurans survived for 10 days. These guys are tough.

But now astrobiologists will want to take a closer look at N. magadii, to see if they're as hardy as D. radiodurans. The team writes, in the paper: "Much longer exposure times need to be tested to see if at least a small number of cells of N. magadii and D. radiodurans could survive the V-UV and vacuum damages present in space without any protection."

Studying to see if microbes have the ability to survive in space conditions has many applications in astrobiology. "For example, it is important to develop planetary protection procedures, life support systems and energy fuel cells based on a number of microbial species," the team writes.

"It is also important to avoid forward contamination," they conclude. You don't want to discover life on Europa, claim it's aliens, but later find out it's just life from Earth that's hitched a ride to Jupiter on a meteorite or a spaceship.

 by "environment clean generations"

If Dinosaurs Were Alive Today?

You're ready to leave work for the day, but before you do, you need to check the traffic report. The concrete jungle doesn't just come populated with predatory drivers these days; dinosaurs were recently resurrected and boy, have they thrived. Just last week, a Tyrannosaurus rex took it into his head to stampede during rush hour, kicking buses and taking bites out of some of the smaller cars that crossed his path. If he's still roaming along your regular commute, you'll plan another route.

OK, let's back up a bit since that scenario is a little far-fetched. How about we consider the question: What if dinosaurs were alive today? Well, technically, many scientists would argue that dinosaurs are alive in modern times. In fact, you probably see them every day since birds are descended from dinosaurs. Minuscule avians like flittering hummingbirds might make a disappointing sight if it was the mighty reptilians of the prehistoric age you were hoping for, but that's what evolution and extinction events have dictated.

But back to our scenario: Researchers have toyed with the idea of recovering preserved DNA and cloning long-dead dinos, à la "Jurassic Park," but it's a challenging proposition. In Japan, efforts are under way to try to clone a woolly mammoth -- extinct only some 8,000 years -- and even that project is proving prickly [source: Macrae]. Most dinosaur species haven't walked the Earth in about 65 million years, so the chances of finding DNA fragments that are robust enough to resurrect are slim. 

Not to mention the many other mile-high procedural obstacles in the way. Going back to a "Jurassic Park" scenario, let's say scientists recovered a bloodsucking insect locked in amber dating from a time when dinosaurs roamed the Earth. 

The potential for cross-contamination both from the entrapped insect itself (which, after all, would likely contain gut flora and the blood of other victims) or from modern organisms the specimen had come into contact with, means very little suitable dinosaur DNA would likely be recovered. If a specimen were cracked open -- assuming it hadn't rotted hollow -- it would be incredibly trying to distinguish the sources of any DNA it contained.

So, chances aren't great we'll ever need to worry whether roaming herds of theropods will disrupt our rush-hour commutes. Or even get to marvel in wonder at specimens concocted in labs occupying prime zoo real estate. After all, if dinosaurs were alive today, their immune systems would probably be ill-equipped to handle our modern panoply of bacteria, fungi and viruses. The chasm is just too large to make that a likely possibility.

On the next page, we'll explore a thornier side of the question: What if dinosaurs hadn't been almost universally wiped out some 65 million years ago when the Chicxulub meteor hit? Would they still be around today? Would we?

So what if the deadly Chicxulub meteor had missed Earth entirely, and dinosaurs hadn't been largely wiped out 65 million years ago? It was only after that impact called an end to dinosaurs' planet-wide party -- which had been taking place for millions upon millions of years -- that the way was paved for mammals to diversify and thrive in the void. Before that, mammals had never really moved beyond the ranks of rodentlike creatures, but once the dinosaurs died off, many species gradually evolved characteristics that were more closely and consistently aligned with what we consider staple mammalian features [source: Smithsonian National Museum of Natural History]. Gradually, primates developed, though it would still be many millions of years before anything really resembling a human was on the scene.

It's impossible to say for sure whether people would now be pounding the pavement if dinosaurs hadn't fallen prey to that unexpected cosmically conceived shakedown. It's entirely feasible that if that catastrophe hadn't occurred, dinosaurs would still be alive today, and we mammals would still be small, burrowing creatures, quaking in fear of the terrible lizards that stalked our land.

On the other hand, it was another extinction event -- the one about 250 million years ago that marked the line between the Permian and Triassic geological periods -- which allowed the dinosaurs their shot in the spotlight in the first place [source: Choi]. So perhaps if Chicxulub hadn't struck, a different calamity would have caused the curtain to fall on the time of the dinosaurs, allowing mammals the chance to jump to the forefront.

Or perhaps the twists and turns of evolution would have followed an entirely different course. Who can say?
Because it's also important to remember that even seemingly simple things like slight alterations in climate or atmospheric composition can trigger small but drastic changes in living conditions, and while some species adapt, others languish. So perhaps an ecological balance would have eventually been struck between mammals and giant reptiles, and we might have evolved in tandem with them, without their untimely extinction. What that alter reality would have looked like, however, remains shrouded in mystery.

 by "environment clean generations"

Early Life Crippled By Natural Nukes

Ancient nuclear reactors buried in lake and shallow ocean sediments may have cooked early microbes, according to a new study. And radiation from the deposits could have delayed the onset of our modern-day, oxygen-rich atmosphere, and even had a hand in shaping the genetics of primordial life.

Natural nuclear reactors dating to 2 billion years ago have been found in Gabon, Africa. Though long since exhausted, scientists know from the unusually low quantity of the Uranium-235 isotope in the rock that they once went critical, and hosted a sustained fission reaction that went on for as long as two hundred thousand years.

A billion years earlier, such deposits could have been common, say Laurence Coogan and Jay Cullen of the University of Victoria. The first oxygen-producing bacteria colonized lakes and shallow seas, and likely created oxygen 'oases' in an otherwise nitrogen-dominated world.

"Oxygen oases would have been hot spots for uranium concentration," Cullen said, because oxygen dissolved in water would draw uranium out of rocks and sediments. "Back then, there was so much more 235U that a softball-sized chunk of uranium would be enough for it to go critical."

If the researchers are right, wherever there were oxygen-producing bacteria, there were also natural nuclear reactors. Radiation could have damaged the bugs' DNA, either directly from the reactors or as leftover atoms of radioactive strontium (Sr) and iodine (I) made their way into the food chain.

 Igneous rocks on Iceland. Ancient nuclear reactors buried in lake and shallow ocean sediments may have cooked early microbes, according to a new study. (image right)

In short, organisms that produced oxygen 3 billion years ago were shooting themselves in the foot by spawning toxic nuclear reactors. That may explain why it wasn't until around 2.3 billion years ago that oxygen finally started building up in the atmosphere. By then, Cullen said, most of the readily available nuclear fuel was used up.

However, it's also possible the reactors had a positive effect on early life.

"Modern cyanobacteria are quite good at dealing with ionizing radiation," Cullen said. "The question you have to     ask is, 'Why?' Well, maybe there was some selective pressure back then that forced them to develop that resistance."

The researchers' work was published in the latest issue of the journal GSA Today.

Radiation is harmful because it causes uncontrolled mutations in organisms' DNA. But mutation is also the engine of evolution. Cullen said it's possible that natural nuclear reactors may have molded the genetic makeup of early life forms. 

"There is no doubt that sources of radiation from geology, the sun, or cosmic rays will definitely cause mutation, and they were almost certainly all higher back then," Paul Falkowski of Rutgers University said.

One way to test that model might be to test ancient rocks for concentrations of lead (Pb) that would indicate whether or not natural nuclear reactors were common in antiquity.

 by "environment clean generations"