LPSC 2017 Trip Report, 3/4

[To the previous chapter][To the beginning]
BISMUTH TELLURIDES AND SULFIDE MIXTURES AND THEIR RELATION TO METAL FROST ON VENUS

In some radar images of Venusian highlands, there is something that looks almost like a snow. Of course, at 500 degrees Centigrade, that must be something else. Something with high reflectivity and high dielectric constant. Probably of an almost metallic nature. What could that be?


[“Snow” in Maxwell Montes on Venus. Image Credit: NASA/Magellan]

The authors hypothesized that this could be tellurides or sulfides-tellurides of Bismuth (Bi2Te3, Bi2Te2S).  They recreated Venusian conditions in the lab to test how these compounds sublimate and interact with CO2-rich Venusian atmosphere, and whether they would, like our snow, make “frost” in Venusian mountains at 300-degree “coldness” out there.

Their conclusions did not look very solid to me, and I’m not sure why only these two compounds were tested with quite many alternatives potentially imaginable. But the notion of “semiconductor snow” has certainly resonated within my mind, so I’ll keep that publication in the list.


[Sulfide-telluride of Bismuth Bi2Te2S, also known as telluric bismuth. Image Credit: Wikipedia]

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THE BIOPAUSE PROJECT: BALLOON EXPERIMENTS FOR SAMPLING STRATOSPHERIC BIOAEROSOL

Whoever have read Michael Chriton’s The Andromeda Strain would immediately appreciate this work. The idea is the same: go as close to the outer space as possible, scoop life samples from out there and bring them back to study. Why? To see how far the Earth’s live continues into space, and what it is like there.

Of course, many countries and organizations have conducted these studies over the past 70 years. USSR, for example, have brought microorganisms from altitudes of 48-77 kilometers back in 1976. But Japan Aerospace Exploration Agency (JAXA) is notable for coming up with new interesting projects for rather modest money.

Typically, such research relies upon cultivation of specimens for analysis. Obtain, seed, grow, study what has germinated. But, according to the author, “more than 99% of the microbes in nature are thought to be uncultivated species” (++another link). So cultivation-based analysis is bound to miss 99% of the catch’s biological diversity – including perhaps the most bizarre and unusual microbes.

To work around that problem, JAXA decided to not cultivate. Instead, they simply studied all collected samples with a fluorescence microscope and a scanning electron microscope. And even though their balloon brought the microbes from a relatively “modest” altitudes of 13-27 kilometers, they (according to the abstract) “estimated the number density of stratospheric microbes including those that cannot be cultivated for the first time in the world.”

Unfortunately, during the mission return they’ve lost the negative test chamber. So the next flight, tentatively scheduled for June 2017, should help with verifying the results.

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SURVIVABILITY OF RNA AND PROTEIN MONOMERS AGAINST EFFECTS OF SHOCK PRESSURES

Suppose a meteorite contaminated with terrestrial DNA hits another planet. Explosion, pressure spike, instantaneous heating — would organic matter survive such an ordeal?

Sometimes there the best way to find out is to run an experiment. That’s what the authors did. They shot artificial “meteorites” with proteins and RNA fragments added against solid targets and measured how much of the organic matter survived impacts. It turns out, rather little:

Shock stress – (approximate impact velocity) — % of organics survived

10.5 GPa — (~2.2 km/c) — 4.3%
28 GPa — (~4 km/c) — 0.7%
40 GPa — (~6 km/c) — 0%

Does that mean that panspermia does not work? Not at all. It’s possible to imagine numerous less stressful ways of organics delivery by meteorites. However, a direct impact against a body the size of Mars without significant slowdown by atmosphere is apparently fatal even for relatively simple organic molecules.

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PULMONARY INFLAMMATORY RESPONSES TO ACUTE METEORITE DUST EXPOSURES – IMPLICATIONS FOR HUMAN SPACE EXPLORATION

Again, this area of research isn’t new. I vaguely remember some papers from 1990s concluding that lunar dust is harmful for lungs and causes strong silicosis in rats.

In this study, inflammatory stress response of human lung tissue to lunar, Martian, Vestian and terrestrial dust was measured. The first three were obtained from corresponding meteorites. The last one was made from terrestrial basalts.

The observations are rather gloomy. All dust caused significant negative effect on lungs. But the worst of four types studied was the dust from Mars. Its effect is comparable to that of terrestrial mine tailings, notable for causing severe health problems in mine workers. Lunar dust is the next, followed by least harmful terrestrial basalts (although they weren’t completely benign, to be clear).


[Inflammatory Stress Response to various types of dust. Image Credit: A.D. Harrington, F.M. McCubbin, J. Kaur, A.Smirnov, K. Galdanes, M.A.A. Schoonen, L.C. Chen, S.E. Tsirka, T. Gordon / NASA Johnson Space Center; Dept. of Environmental Medicine, New York University School of Medicine; Dept. of Geosciences, Stony Brook University; Geology Dept., Lone Star College; Environmental Sciences Dept., Brookhaven National Laboratory; Pharmacological Sciences, Stony Brook University]

I can see several implications here. First, if humans would ever walk on Mars, they would have to invest considerably into protecting against dust there. Second, my pile of paper sheets with imprecisions noted in “The Martian” just grew one item larger :) Third, we often underestimate seriousness of dust effects on other planets. For example, Lunar dust is so strongly abrasive that it destroys moving parts and surfaces exposed to it an order of magnitude faster than what’s expected on Earth. If interested, take a look at the last passage on the 5th page of this document.

To part 4/4.

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