Extraterrestrial life

Inside an astrobiology meeting, with Rob Sheldon

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Dr Sheldon
Rob Sheldon

Physicist Rob Sheldon attended the 17th SPIE Astrobiology Conference (San Diego, 9 – 13 August 2015, and kindly writes to report,

The conference was begun in 1996 when the late David McKay, a meteoriticist from NASA Johnson SFC in Houston, examined a meteorite collected from an expedition to the Allen Hills of Antarctica. The Japanese had discovered that meteorites that land in Antarctica are carried by the ice flow to the foot of mountains where the ice evaporates and meteorites collect. The harvest from annual expeditions are catalogued and stored in Houston, and ALH84001 was the first one collected on this trip.

 

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So this conference was initiated by then SPIE president Richard Hoover, as a forum to present and discuss controversial topics in Astrobiology.

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This type of meteorite, a shergottite, is widely believed to have come from Mars–expelled off the surface by impact, wandering some 1 million years in space (determined by the cosmic ray isotopes on its surface) and arriving a few thousand years ago in Antarctica. The meteorite had micro-fossils, bio-signatures that on earth are attributed to life. Little magnetite grains in peculiar shapes made by magnetotactic bacteria, carbonate bubbles made by respirating bacterial ooze, polycyclic aromatic hydrocarbons from the decay of chlorophyll, and a little “worm-shaped” fossil that was subsequently a media star.

David’s paper caused a furor, and many (contradictory) theories were proposed to explain away one of the features as non-biological, “abiotic”. However when he wanted to publish rebuttal papers with even better pictures, no journal would accept his manuscripts. So this conference was initiated by then SPIE president Richard Hoover, as a forum to present and discuss controversial topics in Astrobiology.

I met Richard in 2002 when he gave a presentation at NASA/MSFC that was riveting. He had purchased several “carbonaceous chondrite” meteorites (remnants of comets) off the internet, taken them to the scanning electron microscope at MSFC and carefully cracked them open to examine their pristine interiors. Richard wanted to avoid all criticism of either contamination or “preparation artifacts” and had put his naked samples in the SEM. The pictures were astonishing. Assemblages of beautifully preserved cyanobacteria, layered exactly as they were in bacterial mats or in living stromatolites, all infilled by water soluble minerals such as MgSO4. Evidently the polysaccharide sheaths that surround cyanobacteria had converted to keragen, and acted as flexible molds for the precipitation of minerals out of water solution. Previous examination of meteorites usually involved “acid maceration” to remove the minerals which unfortunately also removed the fossils, which is why no one had noticed them before.

“But you are requiring that comets have water on them!” I protested, “Everyone knows space is too good a vacuum for liquid water to form. The ice turns immediately into vapor.” Richard was adamant. “The data do not lie. There must be water on comets.” Nor was I going to permit crackpot theories to proliferate. “If what you say is correct, Richard, then comets will behave very differently from asteroids. They should not nutate, but have fixed rotation axes in space. They should show thermal hysteresis, expelling jets for a longer time on the outward leg than the inward leg of their orbit. They should even occasionally explode from the steam pressure.” “Why don’t you look into it?” was Richard’s reply. So I borrowed three comet books from his library, some from the pre-Halley’s-comet era, and some post-Halley. Because the comet’s glowing (from reflected sunlight) dust and vapor coma extends a hundred thousand miles, it is absolutely impossible for ground-based telescopes to peer through this veil to see the 5-10 km nucleus inside. The first ever mission to a comet, the 1986 armada to Halley’s comet revealed that the comet itself was jet black, as dark as soot, making it even less visible to Earth-based telescopes. And the books all said the same thing–comets don’t behave like asteroids, but in fact, show stable spin axes, show thermal hysteresis, show a strange fragility to breakup, show odd dust/vapor ratios. The only theory that explained all these peculiarities, was the one everyone was avoiding–liquid water existed on comets.

We wrote a paper together in 2004, and in 2005 I attended my first Astrobiology conference. In subsequent years we had multiple comet flybys, one comet impacter, and this year, a comet lander, and I presented papers in 2006, 2007, 2008, 2011, 2012, 2013 and this year. With this flood of new information, the “wet-comet model” was confirmed 6 times over. But it wasn’t enough to prevent disaster when the Rosetta mission to Comet 67P/C-G tried to land the dishwasher-sized Philae probe on the surface, and instead of the fluffy snow predicted by the 1950’s Whipple model, they found the concrete we had been predicting. Their harpoons didn’t penetrate, the lander bounced twice and got lost in a crevice nearly upside down. The solar panels didn’t recharge the batteries, nor did the drill find anything to engage, and after 90 hours the batteries gave out. Very little information was returned, and as the day of closest approach–August 13–came and went, it was pretty clear that the solar panels would never recharge the batteries. I hated to say “I told you so”, but I did have a prediction paper about the concrete rejected by Nature. I was even involved in the Rosetta/Rosina planning back in 1992 when I worked for the Swiss, though of course, we hadn’t proposed the wet-comet model until after Rosetta launched, but it might have changed their protocol.

So what was this year’s meeting like? We heard the discouraging news about Philae in a plenary meeting given by a NASA manager with no Rosetta scientists. The manager was exuberant about the engineering success; I was despondent over the scientific failure. So in our session, we examined some of the carbonaceous chondrites of recent vintage — Polonnoruwa 2012 was still being analyzed, as well as Tissint 2011 and the old workhorse of Murchison 1969. To everyone’s surprise, anaerobic bacteria was cultivated from sterile samples of Polonnoruwa and Murchison. To my knowledge, Louis Pasteur had been the first to attempt cultivation of bacteria from carbonaceous chondrite Orgueil 1864, but without success.

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My antagonists were swift–was I denying common descent? No, I replied, I was simply denying Darwin’s assumption that similarities of shape had something to do with time; that no amount of physiology or genetic cladistics can give us information about true history, about actual events in time, since many mechanisms including horizontal gene transport (HGT) would randomize the connections.

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Why then had Elena Pikuta been successful on her first try? Elena showed microscopic pictures of the powdered Murchison using a live/dead stain that caused spores to glow green. Ten or more spores could be seen in this photo, and Elena thought that at first she had been given a purposefully contaminated meteorite. (Not the first or second time this trick had been pulled.) But when 16S sequencing of the organism turned out to be a rather unusual but classifiable bacteria, she changed her mind. She mentioned that this sample of Murchison was light brown, unlike the other blackened stones, and that the high density of spores was quite unusual.

The cultivation of Polonnoruwa produced additional odd but classifiable bacteria. To contrast these extraterrestrial samples, she showed some extremophiles from the highly stratified Lake Untersee found in the Antarctic (on land colonized by the Nazis in 1930s). The extremophile which was a new genus was strange–0.15 x 5 micron rods, thinner than Spirochaeta, while the extraterrestrials were familiar looking rods. Was this what we expected?

I argued yes, and two other participants argued no (which they took as evidence for obvious contamination).

It was a raging 1 hour debate. If Darwin says life evolves from non-life, then we would expect all Earth life to look similar, but ET life to look strange. I argued that the cometary biosphere was vast and extremely ancient. So similar environments should look similar, dissimilar environments will look divergent and neither space nor time should matter. Colonization has homogenized all locations, but time has optimized all micro-environments.

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Darwin’s dogmas have so infused even this bunch of radicalized biochemists that this was a bridge too far. If ever I needed proof that metaphysics organizes our thought and our theories, this was one of those moments.

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My antagonists were swift–was I denying common descent? No, I replied, I was simply denying Darwin’s assumption that similarities of shape had something to do with time; that no amount of physiology or genetic cladistics can give us information about true history, about actual events in time, since many mechanisms including horizontal gene transport (HGT) would randomize the connections. It was almost amusing to watch the puzzlement, as if I had declared the law of gravity to be an opinion. Darwin’s dogmas have so infused even this bunch of radicalized biochemists that this was a bridge too far. If ever I needed proof that metaphysics organizes our thought and our theories, this was one of those moments.

Tissint was a large Martian meteorite (shergottite) that landed in Morocco in 2011, and was found on the Sahara desert a few weeks later. Jamie Wallis showed us cross-sections with many of the same biomarker features David McKay had shown in ALH84001. In addition, there were these strange carbon globules of about 10 micron diameter that turned out to be bags of iron pyrite. As my Kentucky childhood taught me, pyrite is often found in the vicinity of coal seams, so it is a biomarker. But why this shape? Well as it turned out a close terrestrial analogy to meteoritic magnetites was a magnetotactic bacteria found deep in South African gold mines that ate sulfur and made magnetic pyrites. Sulfur is right below Oxygen in the periodic table, and one iron sulfide (Fe3S4 Goethite) is as magnetic as Fe3O4 magnetite.

“Did you test these nodules for magnetism?” I asked. “No,” he replied, he had simply assumed it was the non-magnetic mineral FeS2. “If it’s magnetic”, I told him, “it’s a slam-dunk biomarker.”

So for me the highlights of the meeting were the (unfortunate) confirmation of the wet-comet model, two organisms cultured from meteorites, more evidence of life on Mars, and of course, my daughter’s first presentation at a scientific meeting. Her science fair project was a DC-glow discharge plasma in a bell jar around a Neodymium-Iron-Boron magnet, with the addition of a braided copper wire “accretion disk” around the equator. She showed that the glow became more and more elongated as she raised the electric field strength (magnet voltage – wire voltage), just as astrophysical jets form around magnetic stars with collapsing accretion disks. Young stars that are just being born have thick dusty accretion disks, and jets pumping out material at several 100 km/s. Her experiment is the first to exhibit the behavior of the “central engine” of astrophysical jets, whose speed was exactly what was needed to send bacterial spores to nearby solar systems without too much damage from galactic cosmic rays. Svante Arrhenius was vindicated by Hannes Alfven. There’s something poetic about that.

The remainder of the talks looked at the biochemistry of OOL–how to form RNA abiotically. Sutherland’s group in the UK had abiotically made RNA with phosphate buffer, but Steve Benner did the same with a borate buffer in fewer steps, proposing Mars as the ideal location for OOL. George Fox gave us several talks on ribosomal RNA and the attempt to elucidate its ancient archetypal form. Vera Kolb gave us lectures on coacervates and chemical reactions that happen “on” water, but not “in” water, which may solve the mystery of how water is both a poison and a catalyst for abiotic peptide production. The group at CUNY sent us plots of the sulfases of archaeobacteria analysed for their information content–fractal dimension versus Shannon entropy–arguing that the more recent the DNA, the more “compressed” the DNA instructions. I gave a talk on how primordial comets from the Big Bang could solve not just the dark matter problem and the Origin-of-life problem, but perhaps even the Lithium 7 abundance problem, however, it would require a recalibration of the BB GeV-era that produced protons and neutrons, requiring a massive magnetic field produced by neutrinos–which wasn’t all bad if the magnetic field replaced BB “inflation” while simultaneously solving the missing anti-matter puzzle.

And of course Richard Hoover gave his usual picture show, including pix of Pluto, with its similarity to Europa and Enceladus and the likelihood that Pluto has life. He showed pictures of all the planets, even water ice on Mercury. So from Mercury to Pluto, every planet shows biomarkers, indications of life.

Venus, surprisingly, was the planet that 60 years ago everyone was most certain to have life because it was the twin of Earth, and yet after the space age, it is now the weakest case for life. But then, a month ago, no one thought there would be organics on Pluto either. Our solar system is still full of surprises.

Over breaks we discussed the new openness at NASA to discuss biomarkers on Mars: papers on chloromethane and liquid water were finally being published. “Perhaps,” as I told my wife, “the small size of the meeting this year is an indication that what was once fringe is now being incorporated back into the mainstream. Perhaps our success is also our demise.”

It wouldn’t be the first time that victory required annihilation.

Let’s hope the conference papers are put on line.

See also: Maybe if we throw enough models at the origin of life… some of them will stick?

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3 Replies to “Inside an astrobiology meeting, with Rob Sheldon

  1. 1
    daveS says:

    I also hope the papers will be freely available soon.

    Edit: Especially those describing bacteria cultured from meteorites (presumably extraterrestrial?). That would be amazing, if it holds up.

    However, contrary to this:

    But then, a month ago, no one thought there would be organics on Pluto either.

    researchers found evidence of organic molecules on Pluto as far back as 2011.

  2. 2

    Two typos:
    “mutate” ==> “nutate”, the motion of a nodding, while spinning, top.
    “Jackie Wallis” => “Jamie Wallis”. Sorry Jamie. If you search on Cardiff University, you’ll find his PhD thesis on both Tissint and Polonnoruwa. Great thesis.

    Publication is in the SPIE Proceedings, which have abstracts visible on the web, but papers are behind a paywall. I’ll post free versions on my website: http://rbsp.info/rbs/RbS/ as soon as I get them done.

  3. 3
    News says:

    Both typos now fixed.

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