Researcher sees possibility of Moon life

July 23, 2018, Washington State University
Galileo spacecraft surveyed the moon on Dec. 7, 1992, on its way to explore the Jupiter system in 1995-1997. Credit: NASA/JPL/USGS

While the Moon is uninhabitable today, there could have been life on its surface in the distant past.

In fact, there may have been two early windows of habitability for Earth's Moon, according to a study online today in the journal Astrobiology by Dirk Schulze-Makuch, an astrobiologist at Washington State University.

Schulze-Makuch and Ian Crawford, a professor of planetary science and astrobiology at the University of London, say conditions on the were sufficient to support simple lifeforms shortly after the Moon formed from a debris disk 4 billion years ago and again during a peak in lunar volcanic activity around 3.5 billion years ago.

During both periods, planetary scientists think the Moon was spewing out large quantities of superheated volatile gases, including water vapor, from its interior.

Schulze-Makuch and Crawford write that this outgassing could have formed pools of on the lunar surface and an atmosphere dense enough to keep it there for millions of years.

"If liquid water and a significant atmosphere were present on the early Moon for long periods of time, we think the lunar surface would have been at least transiently habitable," Schulze-Makuch said.

Apollo 16 metric camera image of the Moon's eastern limb and far side. Credit: NASA
Ingredients for life

Schulze-Makuch and Crawford's work draws on results from recent and sensitive analyses of and soil samples that show the Moon is not as dry as previously thought.

In 2009 and 2010, an international team of scientists discovered hundreds of millions of metric tons of water ice on the Moon. Additionally, there is strong evidence of a large amount of water in the lunar mantle that is thought to have been deposited very early on in the Moon's formation.

The early Moon is also likely to have been protected by a magnetic field that could have shielded lifeforms on the surface from deadly solar winds.

Space-travelling microbes

Life on the Moon could have originated much as it did on Earth but the more likely scenario is that it would have been brought in by a meteorite, Schulze-Makuch said.

International Space Station can be seen as a small object in upper left of this image of the moon in the early evening of Jan. 4 2012. Credit: NASA

The earliest evidence for life on Earth comes from fossilized cyanobacteria that are between 3.5 and 3.8 billion years old. During this time, the solar system was dominated by frequent and giant meteorite impacts. It is possible that meteorites containing simple organisms like cyanobacteria could have been blasted off the surface of the Earth and landed on the Moon.

"It looks very much like the Moon was habitable at this time," Schulze-Makuch said. "There could have actually been microbes thriving in water pools on the Moon until the surface became dry and dead."

Lunar simulations

Schulze-Makuch acknowledges that determining if life arose on the Moon or was transported from elsewhere "can only be addressed by an aggressive future program of lunar exploration."

One promising line of inquiry for any future space missions would be to obtain samples from deposits from the period of heightened volcanic activity to see if they contained water or other possible markers of life.

In addition, experiments could be conducted in simulated lunar environments on Earth and on the International Space Station to see if microorganisms can survive under the environmental conditions predicted to have existed on the early Moon.

Explore further: Mineral in lunar meteorite suggests water was once on the moon

More information: Dirk Schulze-Makuch et al, Was There an Early Habitability Window for Earth's Moon?, Astrobiology (2018). DOI: 10.1089/ast.2018.1844

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10 comments

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TheGhostofOtto1923
5 / 5 (6) Jul 23, 2018
Fossils on the moon - so much to look forward to.

We didnt know whether planets existed elsewhere and the boom! there were dozens, hundreds of them. We'll probably see the same thing with evidence for life past and present.
gcyrillus
1.8 / 5 (4) Jul 23, 2018
Is this article telling us that once, there was around the moon an atmosphere with enough pressure to keep water over the triple point (and of course below the critical point) so water could remain liquid on its surface and then that earth's life took a ride there ?

Okay, i got scared they'd say life came from the moon ;)

If water is everywhere, it seems very rare to find it elsewhere than earth in a liquid state for eons.
danR
4 / 5 (1) Jul 23, 2018
Yes, the T and P dynamic would be rather complicated, but starting with the purported ocean and a vacuum and T=0.0, the 'atmospheric' pressure would equilibrate at ~5 Torr.
Being a GHG, the vapor would start trapping heat, raising T, and atmospheric pressure would rise, increasing the water vapor and greenhouse forcing.

That's one crude first approximation, I have no idea what the 'starting' temperature would be, let alone what the opening starting conditions would be, preceding the ocean, but frankly I think the vast bulk of outgassed water would be stripped away by the solar winds, magnetic field notwithstanding.

Finally, I have yet to see a physics-principled model that would allow any biologically active material to be lifted off the earth by an asteroid strike. I don't see any chain of transfer of energy from impact to ejecta, in so strong a gravitational field as Earth's, without involving shock-melting in the final rock sufficient for escape-velocity.
danR
2.3 / 5 (3) Jul 23, 2018
Here's an example of papering-over-a-crack that I'm alluding to:

Rummaging through Earth's Attic for Remains of Ancient Life
Armstrong, J. C. et al., 2010

"...the inner planets experienced frequent large impacts. Material ejected by these impacts near the escape velocity would have had the potential to land and be preserved on the surface of the Moon."

Material ejected. Just like that. Oh, a big asteroid slammed into the earth and by sheer impact lifted great boulders, rocks, trees, proto-Republicans etc. from 0 to 10 km/s in seconds' worth of acceleration. I'm not buying it. I'm seeing shock-melting of it... ALL of it, from viruses to amoeba, from impact to ejecta.
torbjorn_b_g_larsson
2.3 / 5 (3) Jul 24, 2018
Interesting that they see two periods akin to Mars, an initial one after crust formation and a later one after volcanic peak activity.

@danR: The ejection mechanism is spallation - shock wave ejection of crust material - and ejection through the low pressure region that a large hypervelocity impactor left. I think that is robustly modeled and it is the basis for the estimate that Earth life could seed out to Saturn's moons. (Further than that the spherical shell has a too low density rate of ejecta vs moon areas and system time to achieve likelihoods ~ 1.)

I don't think spallation has any melting at all since it is not primary shocked but thrown off by the shock waves moving through deeper layers. And transit through the low pressure regions should mean a meteorite like fusion crust at most -an inverse "meteorite" - the innards still being room temperature (until flash frozen).

I am not buying your shock melting, first time voiced idea, not tested or even published. ;-)
torbjorn_b_g_larsson
2.3 / 5 (3) Jul 24, 2018
Thinking further, who says shock waves through rock melt the material at all?

For impactors it is the failure of waves that does close to an impactor zone. (Energy not dispersed due to sound waves too slow. Dunno about the shock waves.) But spallation happens outside the impact melt zone, possibly many kilometers away at that.
Jayded
not rated yet Jul 24, 2018
You wouldn't need to eject biological material from earth if the moon was once a part of earth.
danR
1 / 5 (1) Jul 24, 2018
spallation.

"...not buying your shock melting, first time voiced idea, not tested or even published. ;-)"


1st off, the literature is stuffed with shock melting; why wouldn't you google it, let alone Google Scholar it:
_________
Shock melting and vaporization of lunar rocks and minerals ...

TJ Ahrens - ‎1972
The entropy associated with the thermodynamic states produced by hypervelocity meteoroid impacts ...
_______

2nd, spallation involves small, brittle, objects where even very small velocities suffice to 'chip-off', so to speak, a chunk of material, and and can involve little or no heating whatsoever. It is the primary source of wear for ball-bearings, for example.

Furthermore, you've illustrated the problem: no physics-principled citations. I took up the question once with one of my profs, and he could provide no sources. I need at least a physics-rigorous computed simulation, not hand-waving explanations. We're back to square one.

danR
not rated yet Jul 24, 2018
You wouldn't need to eject biological material from earth if the moon was once a part of earth.

That would entail an (unlikely) post-biotic earth scenario.
barakn
not rated yet Jul 24, 2018
How ironic that danR would accuse others of not doing literature searches. Spallation has several different but related meaning. Start with
"Impact ejection, spallation, and the origin of meteorites" H.J. Melosh, Icarus
Volume 59, Issue 2, August 1984, Pages 234-260 (with 221 citations!) and follow up with "The Rocky Road to Panspermia," H.J. Melosh, Nature, Volume 332, April 1988, Pages 687-688.
The spalled material comes from material a significant distance away from the center of the impact, and the largest impacts are the most productive. I take slight issue with torbjorn's statement that spallation comes from "shock waves moving through deeper layers." More precisely, it occurs in near-surface material resulting from a combination of primary and secondary shock waves.

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