I think a lot of the questions asked below were answered by the article, but others obviously feel differently. Here's my interpretation of the answers based on my interpretation of the article and past reading. Please excuse any typos, they are worse than normal as I am obviously rusty.

Marsbug & Phil:

The article mainly focuses on Mars, but I'd say any of the bodies known or suspected of liquid water at some depth would be possibilities. I'd say Europa, Ganymede, Callisto, Titan, and Enceladus are all prime candidates if the origin of life was underground. The E moons were specifically mentioned. There are also other moons with hints of geologic activity that may be related to water layers if a moon as small as Enceladus can have one. Local panspermia may have spread life to some or all of those even if the origin was on the surface of just one.

Where I could use some help from gelogists is the comment "When you do the calculation, you find out that the rate of chemical recharge on Mars is about 10 times less than it is on Earth,". This seems to imply to me that the biosphere could support only about a tenth of the microbe density as Earth under a similar chemical environment. I'm assuming what they mean is that the radioactivity only regenerates the hydrogen and sulfate the microorganism metabolizes at 1/10 the rate on earth and that the microbe density of a particular organism is proportional to how fast it's food source regenerates.

However I have a problem with that 1/10 th statement. Mars generates radioactive energy and particles relative to Earth in proportion to its mass which is about 1/10 (1/8 volume times density ratio). However I would think the recharge rate would be proportional to the radioactive flux (energy per unit time per unit area) through the relatively thin habitable layer. This would be roughly proportional to (Rm/Re)^3/(Rm/Re)^2 or simplified Rm/Re which is roughly 1 half where Rm = Mars' radius and Re Earths. This is important because all the other possibilities are even smaller than Mars.

Socrates:

The article states the species has been isolated from other life for 3 to 10 million years. If you believe It could have evolved its genome during the period Mars is believed to have been habitable I see no reason it couldn't survive billions of years of Mars in its current state.

Raoul:

As Socrates mentions many scientists believe life may have originated underground. The reason for this is that many deep microbes have diverged more genetically than surface life. An alternative explanation is that life originated on the surface, but only those that migrated underground survived a particularly devastating mass extinction such as a gamma ray burst or large impact.

Phil:

We simply didn't know what to look for. Hydrothermal vent life and deep microbes were discovered long after the Vikings were launched and we have had few missions studying the moons of the outer planets. I believe they were minor targets for Voyager until we discovered the were far more interesting than the fossilized slag heap that is our moon. Regardless, I think we live in a golden age of astronomy and planetology. I can think of all kinds of discoveries over the past 15 years that rival those in text books from my days in school.

Moderators:
Why no note on the deletion of EP's sub thread?

Regards,
Mark