This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Protocells
Whatever else transpired at the time of life’s recognizable origins on Earth it seems likely that a critical step was the formation of cells – membrane enclosures – in which more complex molecules could congregate at concentrations high enough for interesting chemistry to take place. But there’s a catch: salty, ion-filled ocean water and ionic magnesium and iron, present in compounds like RNA, all act to destroy the fatty-acid spheres that we think could have been the first proto-cells. A new study by Cornell et al. offers a plausible and neat solution. It appears that if amino acids are simply thrown into the mix they can not only protect the fatty-acid layers from being destroyed, they can trigger structural changes that include the formation of multi-layer cell walls, much more similar to modern animal cells. There’s a way to go to before we understand this better, but it’s one of the most promising discoveries to come along so far.
Bombardment
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There’s little doubt that the very young solar system, 4.5 billion years ago, was a rather chaotic place. In order to explain the present architecture of the major planets a certain amount of orbital rearrangement, or migration, is often invoked. This is also motivated because it helps explain evidence for a period of intense asteroid bombardment (the Late Heavy Bombardment) that has been thought to occur about 3.9 billion years ago. But some of that evidence, in massive cratering on the Moon, is tricky to interpret due to limited statistics. Now a new study by Mojzsis et al. using modeling and data from meteorites proposes an earlier timeline. In this scenario the giant planets underwent orbital shifts around 4.48 billion years ago, triggering a period of bombardment on worlds like the Earth. Intriguingly, by shifting this tumult to an earlier time the Earth might have been a calmer place for life to get going some 4.4 billion years ago, about half a billion years earlier than commonly assumed.
Martian Erosion
The seemingly sporadic presence of atmospheric methane on Mars, confined to certain locations and altitudes is a subject of intense ongoing study and speculation. Could it be due to methane-producing life, or is it geological in origin? In either case, just figuring out exactly how it’s being released from somewhere on the surface is a key step. A new study by Safi et al. looks at the possibility of wind erosion releasing methane trapped in rocks. It turns out that unless there is methane trapped in deposits rivaling the richest hydrocarbon shale on Earth it’s extremely unlikely for erosion to be producing the pulses of gas detected by instruments like those onboard the Curiosity rover. That’s an extremely important negative result, helping to further narrow the options and allowing us to home in on the truth.
Biofluorescence
Add a new trick to the toolbox used for seeking life elsewhere in the universe. On Earth some ocean corals reprocess damaging ultraviolet light into visible wavelengths, fluorescing with spooky but beautiful red, orange, or green light. Not to be confused with bioluminescence – biofluorescence UV conversion doesn’t involve chemical reactions or the organisms generating their own light, they’re simply juggling the UV photons like hot potatoes until they can ‘cool’ them off. A new study by O’Malley-James and Kaltenegger asks how this kind of mechanism might play out on other worlds, particularly on rocky exoplanets closely orbiting low-mass M-dwarf stars known for their tendency to emit strong flares of UV-light. Remarkably, for a planet covered in biofluorescent life, in the right conditions an incoming flare of ultraviolet radiation could cause a glow response that would temporarily increase the visible light coming from the planet by up to a factor of a hundred. It’s a temporal biosignature that just might be detectable by a new generation of giant telescopes.
