NASA’s teleconference from the Astrobiology Science Conference 2010 in Houston offered some interesting news about the discovery of microscopic fossils in gypsum from a period about six million years ago, when the Mediterranean Sea had all but dried up. Gypsum (calcium sulfate) precipitates out of sea water, and the find has implications for finding life on Mars, as I’ll explain in a moment.
What gave me a chuckle, though, was that after a discussion between four crack astrobiologists about life’s appearance on Earth and the best ways to search for it elsewhere, the first question from reporters was about Stephen Hawking’s views on aliens, and whether NASA had a policy on broadcasts to the stars.
The answer is clearly no, and NASA’s Mary Voytek noted the differences of opinion between the agency’s scientists on the issue, prompting Steven Squyres (of Mars rover fame) to note that our signals are already in play in the form of TV broadcasts and planetary radar signals. I’m thinking that Bill Schopf, who introduced the micro-fossil research, must have been bemused at having his work so quickly trumped. But Schopf (UCLA) and Jack Farmer (Arizona State) are onto something with implications for future sample return missions from Mars, so let’s put Hawking and aliens aside.
Micro-Fossils and Mars
It turns out that little work has been done with fossils preserved in gypsum because, as Schopf said, most scientists assumed that sulfate deposits undergo sedimentary changes that, as with carbonates, would crush such tiny fossils, which is why you don’t, for example, find micro-fossils preserved in limestone on Earth. But it turns out that Schopf and Farmer have found fossils in numerous deposits of gypsum. And the interesting follow-on is that Mars has huge areas at the north pole and the equatorial region near Valles Marineris where gypsum is common. The Opportunity rover, as a matter of fact, landed on a sulfate deposit.
Now that we know that a biosignature can be preserved in sulfates, we can think about mission implications. For gypsum is soft enough to trench with the robotic arm of a rover. It’s also soluble in water. Dissolve away the mineral material and you just might find clumps of organic material and perhaps fossils, all of which was fodder for Steve Squyres’ later discussion of a sequence of three Mars missions, incorporating a rover to collect samples, a lander that would pick them up, and an orbiter that would recover the samples and return the package to the Earth.
Asteroid Ice and Organics
Likewise of astrobiological note (and discussed briefly in the teleconference) were the new papers on the infrared spectra of the main-belt asteroid 24 Themis, which show a frosty coating of water ice and organics on the object. The ice was an unusual find, for at this distance (roughly 480 million kilometers from the Sun), ice is not stable and needs to be replenished. Themis is about 200 kilometers in diameter and it’s possible that replenishment is coming from within, which reminds us of scenarios in which incoming objects brought water to the early Earth.
This BBC story on the asteroid find quotes Andy Rivkin (Johns Hopkins) on the matter:
“Finding ice in Themis and the Themis family opens up the possibility that you might have brought in water from asteroids as well as comets; and that potentially allows a lot more water to be brought in and it also allows the isotopic compositions to work out the way we need them to, to match the Earth.”
That last reference is to the fact that Earth water does not match well with comets as the single origin. Adding icy asteroids to the mix could resolve the complication. For more on this, see Campins et al., “Water ice and organics on the surface of the asteroid 24 Themis,” Nature 464 (29 April 2010), pp. 1320-1321 (abstract) and Rivkin and Emery, “Detection of ice and organics on an asteroidal surface,” Nature 464 (29 April 2010), pp. 1322-1323 (abstract).
SETI Takes the Stage
The Astrobiology Science Conference ends today with morning sessions on biosignatures and the quest for life on Mars. Two SETI sessions have been held to the afternoon, the final one much in the spirit of the Hawking debate that has been raging on the Net all this week. That session is titled “Global Engagement and Interstellar Message Construction.” Chaired by Frank Drake and Douglas Vakoch, it goes into the intricacies of communication between intelligent beings of entirely different evolutionary and cognitive histories. It’s good to see that Jim and Gregory Benford will be discussing their ideas on cost-optimized interstellar beacons — much debated in these pages — in the earlier SETI session. Check the AbSciCon2010 site for abstracts.
Claudio Maccone also called yesterday from Houston. He’s at AbSciCon 2010 with poster presentations on the uses of the Karhunen-Loève Transform in SETI, especially as they relate to fast-moving sources, and our ability to use the KLT in future space communications with our own probes. Maccone’s idea of a ‘radio bridge’ using the gravitational lenses of both the Sun and Alpha Centauri — enabling interstellar communications with no more power than a cell phone — should play well to this audience. For more on the KLT, see this earlier post, and check here for the radio bridge.