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james_davis_nicollSpace: Section Two: Controversy is Rife on Mars
Brand interviews Sagan and Margulis about the implications of the Viking probes for life on Mars.
I'd like to start off with an admission of ignorance: I had no idea Margulis was involved in the Gaia Hypothesis.
Lynn Margulis
Margulis interpreted what was known about Mars before Viking to mean that Mars had no indigenous life. The Viking results appeared to support this:
SB: Well, how's the Gaia Hypothesis, in view of Viking?
Margulis: It's flying. We may be right. It looks like there's no life on Mars.
Something I've wondered about the Gaea Hypothesis: at which point in Earth's history would someone who subscribed to it have predicted that Earth had life, based on the atmospheric data?
Although she is pretty convinced that the results support her model, she does point out that the experiments were designed for a Mars that turned out not to exist and so may not have been the best set to use on the Martian surface (and what exactly the pyrolytic release experiment meant was open to question). No organic material is still no organic material, though.
This touches on an old obsession of mine:
SB: If there were life you'd look for what gases?
Margulis: You'd look for ammonia, methane, hydrogen, or hydrogen sulfide or any of these things that are flagrant contradictions in the presence of oxygen and CO2.
While Mars' atmosphere might be at chemical equilibrium (although I think this is no longer thought to quite be the case), there are bodies in the Solar System whose atmosphere's are not. Something produced methane in Uranus and Neptune and on Titan and since methane is fairly quickly destroyed in all three cases, that something is still producing it. This isn't to say it's life, of course.
Margulis is not optimistic that Mars could be made life-bearing, either. Fogg would later come up with some rather distressing time scales for terraforming Mars, results that are quite unpopular in some circles.
Carl Sagan
Sagan is far more positive about the possibility of life on Mars in light of the Viking results than Margulis. He's even rather perky about the implications of a post-biotic Mars for the development of life. This makes me wonder exactly what his background in biology was at this time (Margulis obviously we all know).
A Mars with patches of isolated micro-organisms would be interesting. Sagan speculates that spores could be spread on the wind but the surface of Mars is pretty hostile to organic material so I wonder if what you might not get are oases that have been isolated from each other for hundreds of millions or even billions of years.
Sagan goes into some detail about the kind of organics Viking couldn't detect, which were the simple ones.
Sagan and Margulis come to opposite conclusions about the age of the surfaces Vikings I and II were looking at: she sees an ancient and unchanging world while he sees one whose surface condition is potentially quite recent.
As I recall the landers outlasted the funding provided to listen to their results on Earth, which caused some sweating on Earth. It would have been embarrassing for Viking I and II to be transmitting to Earth, only to have the data lost because nobody was gathering it here.
While Margulis blamed Mars' low escape velocity for the low air pressure, Sagan blames the climate.
What Sagan calls Mariner Jupiter-Saturn is what became Voyager I and II.
We have no approved Viking follow - on for Mars. Nothing like a lander on Titan, a probe into Jupiter, an orbiter around Venus, a rendezvous with a comet, all sorts of meaty kinds of missions that we're fully capable of and our scientific knowledge cries out for.
We did eventually see most of these, most of them before Sagan's death in 1996: Huygens on Titan (Jan 2005), Galileo's atmospheric entry probe (Dec 1995), Venera 9 (Oct 1975) among other Venus orbiters and in the sense of a fly by, a flotilla of space-craft encountered Halley's Comet back in 1986.
Brand interviews Sagan and Margulis about the implications of the Viking probes for life on Mars.
I'd like to start off with an admission of ignorance: I had no idea Margulis was involved in the Gaia Hypothesis.
Lynn Margulis
Margulis interpreted what was known about Mars before Viking to mean that Mars had no indigenous life. The Viking results appeared to support this:
SB: Well, how's the Gaia Hypothesis, in view of Viking?
Margulis: It's flying. We may be right. It looks like there's no life on Mars.
Something I've wondered about the Gaea Hypothesis: at which point in Earth's history would someone who subscribed to it have predicted that Earth had life, based on the atmospheric data?
Although she is pretty convinced that the results support her model, she does point out that the experiments were designed for a Mars that turned out not to exist and so may not have been the best set to use on the Martian surface (and what exactly the pyrolytic release experiment meant was open to question). No organic material is still no organic material, though.
This touches on an old obsession of mine:
SB: If there were life you'd look for what gases?
Margulis: You'd look for ammonia, methane, hydrogen, or hydrogen sulfide or any of these things that are flagrant contradictions in the presence of oxygen and CO2.
While Mars' atmosphere might be at chemical equilibrium (although I think this is no longer thought to quite be the case), there are bodies in the Solar System whose atmosphere's are not. Something produced methane in Uranus and Neptune and on Titan and since methane is fairly quickly destroyed in all three cases, that something is still producing it. This isn't to say it's life, of course.
Margulis is not optimistic that Mars could be made life-bearing, either. Fogg would later come up with some rather distressing time scales for terraforming Mars, results that are quite unpopular in some circles.
Carl Sagan
Sagan is far more positive about the possibility of life on Mars in light of the Viking results than Margulis. He's even rather perky about the implications of a post-biotic Mars for the development of life. This makes me wonder exactly what his background in biology was at this time (Margulis obviously we all know).
A Mars with patches of isolated micro-organisms would be interesting. Sagan speculates that spores could be spread on the wind but the surface of Mars is pretty hostile to organic material so I wonder if what you might not get are oases that have been isolated from each other for hundreds of millions or even billions of years.
Sagan goes into some detail about the kind of organics Viking couldn't detect, which were the simple ones.
Sagan and Margulis come to opposite conclusions about the age of the surfaces Vikings I and II were looking at: she sees an ancient and unchanging world while he sees one whose surface condition is potentially quite recent.
As I recall the landers outlasted the funding provided to listen to their results on Earth, which caused some sweating on Earth. It would have been embarrassing for Viking I and II to be transmitting to Earth, only to have the data lost because nobody was gathering it here.
While Margulis blamed Mars' low escape velocity for the low air pressure, Sagan blames the climate.
What Sagan calls Mariner Jupiter-Saturn is what became Voyager I and II.
We have no approved Viking follow - on for Mars. Nothing like a lander on Titan, a probe into Jupiter, an orbiter around Venus, a rendezvous with a comet, all sorts of meaty kinds of missions that we're fully capable of and our scientific knowledge cries out for.
We did eventually see most of these, most of them before Sagan's death in 1996: Huygens on Titan (Jan 2005), Galileo's atmospheric entry probe (Dec 1995), Venera 9 (Oct 1975) among other Venus orbiters and in the sense of a fly by, a flotilla of space-craft encountered Halley's Comet back in 1986.
