In a double dose of Martian research, scientists believe that the planet once had the right environmental conditions to support life underground and its moons may have been born from an ancient collision.
NASA boffins are increasingly convinced that the best chances for finding microbial life on Mars is under the surface, and new research backs that up.
“We showed, based on basic physics and chemistry calculations, that the ancient Martian subsurface likely had enough dissolved hydrogen to power a global subsurface biosphere," Jesse Tarnas, lead author of a paper published in Earth and Planetary Science Letters and a graduate student at Brown University in the US, on Monday. "Conditions in this habitable zone would have been similar to places on Earth where underground life exists."
Earth is teeming with microbes. There are a group known as lithotrophs that respire by stripping electrons off inorganic substances like dissolved molecular hydrogen. The researchers believe that radiation from radioactive elements on Mars would have split water in the Red Planet's ancient lakes into separate hydrogen and oxygen molecules.
The process, known as radiolysis, would create enough hydrogen to sustain lithotrophs beneath the planet’s crust. By inspecting data from the gamma ray spectrometer aboard NASA’s Mars Odyssey spacecraft, the researchers calculated the abundance of thorium, potassium, and uranium on Mars and estimated the amount of groundwater to work out if radiolysis was a viable option for life.
"People have a conception that a cold early Mars climate is bad for life, but what we show is that there's actually more chemical energy for life underground in a cold climate," Tarnas said. "That's something we think could change people's perception of the relationship between climate and past life on Mars."
The curious case of Mars' moons
Eggheads have been left puzzled over the origin of Mars’ moons: Phobos and Deimos for a while. Some believe that they are D-type asteroids (chunks of space rock from the outer reaches of the Asteroid Belt) that have been captured after flying too close and others think that is an impossible scenario considering the shapes and orbits of the two natural satellites.
Now a study on the moons introduces another possibility. Phobos and Deimos may actually be fragments of Mars that broke off and were flung into space after a powerful collision event.
Photographs of the moons in the mid-infrared spectrum were compared to heated samples of a meteorite believed to be a chunk of a D-type asteroid that landed in the Tagish Lake, Canada, over 18 years ago.
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“We found, at these wavelength ranges, the Tagish Lake meteorite doesn't look anything like Phobos, and in fact what matches Phobos most closely, or at least one of the features in the spectrum, is ground-up basalt, which is a common volcanic rock, and it's what most of the Martian crust is made out of," said Tim Glotch, lead author of the research published on Monday in the Journal of Geophysical Research – Planets.
"That leads us to believe that perhaps Phobos might be a remnant of an impact that occurred early on in Martian history."
That alone still doesn’t explain its dark colors. Visually, the moons look more similar to D-type asteroids, characterized by very low albedos from the rich carbon and silicates material. Marc Fries, a scientists and curator of cosmic dust at NASA's Johnson Space Center, who was not involved in the new study, said the color of Phobos and Deimos may have changed after over time.
Space dust containing specks of carbon could have settled on the satellites over time, painting them black, the team posit. The results are far from certain, however, Fries said.
“I would not consider this to be a final solution to the mystery of the moons' origin, but it will help keep the discussion moving forward." It’s difficult to replicate the surface of the Moon’s in a laboratory, and the meteorite sample hasn’t been confirmed that it’s from a D-type asteroid.
But Glotch said it’ll be something that will be tested practically in the future as the Japanese Aerospace Exploration Agency (JAXA) plans to bring back a real sample of Phobos.
"The really cool thing is that this is a testable hypothesis, because the Japanese are developing a mission called MMX that is going to go to Phobos, collect a sample and bring it back to Earth for us to analyze." ®