Genesis reloaded: are there forms of life on Earth we’ve missed?

Paul Raven @ 11-11-2010

It’s a well-used riff, but it seems to be making a comeback in recent months: is there a “shadow biosphere” of lifeforms on Earth that don’t obey the known rules of biochemistry? And if so, how might we find it – let alone recognise it when if do? A nice long article; you should go read the whole thing, but here’s a few snippets:

To investigate a species of microbe fully, you first need to culture it in the laboratory and then study its biochemistry by sequencing its genome to position it on the tree of life. This technique, while undoubtedly important, has its problems.

Many microbes don’t like being plucked out of their natural habitat and cannot be cultured easily. Some resist gene sequencing.

And, because the chemical techniques used to analyse microbes are customised and targeted to life as we know it, they wouldn’t work on an alternative form of biology. Should there be a different type of microbial life out there, it is very likely to be overlooked, simply because it would be unresponsive to the biochemists’ probes used so far. In a laboratory sample it might well get thrown out with the garbage.

If you set out to study life as we know it, then what you find will inevitably be life as we know it. It’s therefore an open question whether some microbes might actually be the descendants of a different genesis.

[…]

Notwithstanding their exotic nature, to date all extremophiles that have been analysed are standard life: they belong to the same tree of life as you and me. Their existence proves that the range of conditions under which standard life can survive is much broader than previously suspected. Nevertheless there are limits.

If there is a shadow biosphere, it might be occupied by weird ‘hyper-extremophiles’ inhabiting environments beyond the reach of even the hardiest form of standard life, and have so far escaped detection because nobody thought to look for any form of life under such extreme conditions. A good example is temperature: standard hyperthermophiles seem to have an upper limit of about 130˚C – and for good reason. The intense heat disrupts vital molecules, and even with a host of repair and protection mechanisms, DNA and proteins start to unravel and disintegrate if they are subjected to temperatures much in excess of 120˚C.

Suppose we find nothing living between 130˚C and 170˚C in a deep-ocean volcanic-vent system, but then discover microbes thriving there between 170˚C and 200˚C? The discontinuity in temperature range would be a strong indicator that we were dealing with weird life as opposed to standard life that had simply pushed the temperature envelope higher.

[…]

There are plenty of other places that could be home for isolated weird extremophiles. The inner core of Chile’s Atacama Desert is one place – it is so dry and oxidising that bacteria can’t metabolise. The U.S. space agency NASA has a field station there, but so far there is no evidence for any carbon chemistry that could be attributed to weird life.

Other possible locations include the upper atmosphere, cold dry plateaus and mountain tops (where high-ultraviolet flux is a problem for standard life), ice deposits at temperatures below -40˚C, and lakes heavily contaminated with metals toxic to known life. We don’t need to confine our search to a single parameter such as temperature; it’s possible that some combination such as temperature and acidity together is more relevant.

Very speculative stuff, as science goes: it’s basically hinging on the old “white crow” aphorism, which says that the fact that you’ve never seen something doesn’t prove that the thing doesn’t exist. But we’re friends of informed speculative science around these parts, so… 🙂


Have we found the first habitable exoplanet?

Paul Raven @ 30-09-2010

This story’s pretty much everywhere today, though the headlines would probably be more accurate (if more cumbersome and less exciting) if they said that researchers have located the first exoplanet confirmed to be in an orbit around its parent star that would permit the possibility of liquid-phase H2O on its surface, and to have sufficient mass to hold on to a “substantial” atmosphere.

(Kinda takes the magic out of it, this whole accuracy thing… but it’s still pretty awesome when you think about it. Or it is for me, anyway.)

The new planet is one of six orbiting the star Gliese 581, a red dwarf 20 light-years from Earth. Two of the planet’s siblings, dubbed planets C and D, have also been hailed as potentially habitable worlds. The two planets straddle the region around the star where liquid water could exist — 581c is too hot, and 581d is too cold. But 581g is just right. The discovery will be published in the Astrophysical Journal and online at arxiv.org.

The new planet is about three times the mass of Earth, which indicates it is probably rocky and has enough surface gravity to sustain a stable atmosphere. It orbits its star once every 36.6 Earth days at a distance of just 13 million miles.

[…]

Gravity dictates that such a close-in planet would keep the same side facing the star at all times, the same way the moon always shows the same face to Earth.

That means the planet has a blazing-hot daytime side, a frigid nighttime side, and a band of eternal sunrise or sunset where water — and perhaps life — could subsist comfortably. Any life on this exotic world would be confined to this perpetual twilight zone, Vogt says, but there’s room for a lot of diversity.

“You can get any temperature you want on this planet, you just have to move around on its surface,” Vogt said. “There’s a great range of eco-longitudes that will create a lot of different niches for different kinds of life to evolve stably.”

The inevitable disclaimer here is that although it looks like Gliese 581g could support some sort of life, whether it actually does is still something of a cosmological crapshoot with unknown odds. However, the relative ease with which we’ve found it suggests there may be many more planets in similar situations, which raises the chances of us humans not being the only gang in town after all. Those odds are still pretty long, of course… but hey, we can dream, right? Question is, will we find ’em and meet ’em before time runs out?


Space is the place, redux

Paul Raven @ 07-06-2010

Seeing as how SpaceX managed to pull off the first commercial rocket launch to reach orbit over the weekend, I figure we’re allowed to get a bit excited about space again… it’s a welcome distraction from the World Cup, if nothing else. It might have been even more of a distraction to our antipodean friends, some of whom spotted weird lights in the sky that may (or may not) have been parts of the Falcon 9 falling back to Earth [via SlashDot].

But who can we trust to tell us the truth of it, hmmm? After all, the Chinese have a history of telling porkies about their space program, and hell knows the Cold War space race was all about giving the people the story you wanted them to believe… it might be fun to work as a spin doctor for a multinational space company.

Speaking of the Cold War, did you know that Venera, the Russian mission to Venus, was the first to send back photographic images from another planet? If any nation-state or corporation is taking a poll on where we should send space probes next, my vote goes for Titan – it’d be fun to find out if those atmospheric anomalies are actually the signal of methane-based microbial life that they appear to be


Oxygen not a prerequisite for life after all

Paul Raven @ 08-04-2010

Dust off those life-on-other-planets hard sf stories in your trunks, writer-types, because the subgenre might just have had a much-needed shot in the arm: the oddly-named Zoologger is a little multicellular critter discovered in deep mud in the Mediterranean, and it doesn’t need oxygen for its survival or reproduction.


“We have a moral obligation to seed the universe with life”

Paul Raven @ 10-02-2010

Centaurus A galaxies eruptingThat’s the opinion of Michael Mautner, Research Professor of Chemistry at Virginia Commonwealth University:

As members of this planet’s menagerie, and a consequence of nearly 4 billion years of evolution, humans have a purpose to propagate life. After all, whatever else life is, it necessarily possesses an incessant drive for self-perpetuation. And the idea isn’t just fantasy: Mautner says that “directed panspermia” missions can be accomplished with present technology.

“We have a moral obligation to plan for the propagation of life, and even the transfer of human life to other solar systems which can be transformed via microbial activity, thereby preparing these worlds to develop and sustain complex life,” Mautner explained to PhysOrg.com. “Securing that future for life can give our human existence a cosmic purpose.”

Hasn’t the relentless drive of self-propagation been shown to be somewhat problematic over the long term? Do we need a cosmic purpose? More importantly, does the cosmos need us to have a cosmic purpose? When evangelical ideology and colonialism run out of planetary surface, I guess they have to start looking further afield for things to interfere with… [image via badastronomy]


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