Module 5 - The Search for Life

Life on Venus?

While potential invasions from Mars are common plot elements in movies, invaders from Venus are rare.  (Note: you’ll find some early science fiction depicting Venus as a hot jungle environment and then there is this movie. Since we don't have much in this section, here is the trailer:


If you felt like you "are there" and want to watch the whole thing, here is the link.   And here is the MST3K treatment.

And indeed, a surface temperature of 462°C with an atmospheric pressure equivalent to 1 km water depth, Venus does not seem like a good candidate for life. Venus today does not have a magnetic field, but the very thick atmosphere blocks out cosmic radiation. Venus did not always experience these nasty conditions; early in its history it would have had much more earth-like conditions.  And so the question of life on Venus needs to be restated as “If life had taken hold on an early Venus, is there a setting in which some extremophiles might still be hanging on?

In 2015 a group of British scientists suggested that there is a restricted range in altitude within Venus’ atmosphere, somewhere between 51-62 km, where conditions might be more habitable.  The lower elevation was determined by the observation that no terrestrial thermophilic-hyperacidophiles can tolerate pH of 0 at temperatures above 65 °C, while the upper elevation range has a T= -20°C and still provides enough shielding from cosmic radiation.  The latter is important because Venus does not have an active magnetic field like the Earth, which shields us from much of this radiation.

So, in a nutshell, the chances of life on, or more precisely above Venus are very small.

We don't expect you to read the article on the constraints of life within the Venusian clouds. But if you are interested, you might find the first few sections interesting as they discuss different aspects in very general terms.


SaveSaveUpdate March 2018


The idea that life may have survived within Venusian clouds has been revived by an international team of scientists, Drs. Limaye and Mogul and is published in the journal of Astrobiology (news release).  The new work is centered on the fact that
 

"Venus shows some episodic dark, sulfuric rich patches, with contrasts up to 30-40 percent in the ultraviolet, and muted in longer wavelengths. These patches persist for days, changing their shape and contrasts continuously and appear to be scale dependent," says Limaye.

The particles that make up the dark patches have almost the same dimensions as some bacteria on Earth, although the instruments that have sampled Venus' atmosphere to date are incapable of distinguishing between materials of an organic or inorganic nature.

The patches could be something akin to the algae blooms that occur routinely in the lakes and oceans of Earth, according to Limaye and Mogul -- only these would need to be sustained in the Venusian atmosphere.

Limaye, who has spent his career studying planetary atmospheres, was further inspired to revisit the idea of microbial life in the clouds of Venus by a visit to Tso Kar, a high-altitude salt lake in northern India where he observed the powdery residue of sulfur-fixing bacteria concentrated on decaying grass at the edge of the lake being wafted into the atmosphere.


To test their idea, they propose an aerial mission in which

a craft that flies like a plane but floats like a blimp and could stay aloft in the planet's cloud layer for up to a year gathering data and samples.

Such a platform could include instruments like Raman Lidar, meteorological and chemical sensors, and spectrometers, says Limaye. It could also carry a type of microscope capable of identifying living microorganisms.

"To really know, we need to go there and sample the clouds," says Mogul. "Venus could be an exciting new chapter in astrobiology exploration."
The Wisconsin scientist and his colleagues remain hopeful that such a chapter can be opened as there are ongoing discussions about possible NASA participation in Russia's Roscosmos Venera-D mission, now slated for the late 2020s. Current plans for Venera-D might include an orbiter, a lander and a NASA-contributed surface station and maneuverable aerial platform.

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