The Past and Future Mars

The Past:

Mars has water, and it used to have a lot more.  If modern Mars had the ocean it once had, it would evaporate off into space quickly because there is no heavy atmosphere to help keep it pressurized and in liquid form.  Mars would have had a thicker atmosphere in addition to it’s magnetic field in order to keep all that water in one place.  So where did the atmosphere go? And if there was such a thick atmosphere, how does it account for the fingerprint of excess Carbon-13 and a lack of Carbon-12 found on the red planet today? Astronomers from NASA’s Jet Propulsion Lab (JPL) and the California Institute of Technology (Caltech) may have an answer.

Credit: Lance Hayashida/Caltech Office of Strategic Communications

They have found a photochemical process that accounts for a thick Martian atmosphere while matching the current abundance of isotopes seen on Mars.  It has generally been accepted that the Carbon would have disappeared in one of two ways: Either it was lost to space, or it became trapped in rocks called carbonates.

A recent JPL study using Mars orbital data suggests that there aren’t enough carbonates to account for the missing Carbon. If it was lost to space, how much could have been lost? Astronomers trace this amount by looking at the ratio of Carbon-12 to Carbon-13.  Because Carbon-12 is lighter, it is more readily lost to space.  By looking at ancient Martian meteorites, we can measure this ratio from the past, and compare it to the ratio observed today.  This comparison can give an accurate reading of how the atmosphere has changed over time and give insights into the processes that led to the changes.

The proposed mechanism involves ultraviolet light breaking up a molecule of Carbon Dioxide into Carbon Monoxide and Oxygen Gas.  Another UV photon hits the Carbon Monoxide and breaks it down further into pure Carbon and Oxygen.  Some of the resulting Carbon is Carbon-12 and some is Carbon-13.  The lighter Carbon-12 has a higher likelihood of escaping into space than the heavier Carbon-13, and so we end up with lost Carbon and an excess of Carbon-13.

Working backwards with this mechanism, they showed that ancient Mars may have had an atmosphere as dense as Earth’s, even though it was still mostly CO2.  “The efficiency of this new mechanism shows that there is in fact no discrepancy between Curiosity’s measurements of the modern enriched value for carbon in the atmosphere and the amount of carbonate rock found on the surface of Mars,” says Bethany Ehlmann, assistant professor of planetary science and a research scientist at JPL. “With this mechanism, we can describe an evolutionary scenario for Mars that makes sense of the apparent carbon budget, with no missing processes or reservoirs.”

The Future:

Two weeks ago I wrote a post on the Martian Moon Phobos, discussing how it will likely break into pieces due to the tidal forces of Mars as it lowers its orbit over the next few tens of millions of years.  Well after it does finally break up, it will potentially form a pretty awesome looking ring system.

Mars as a ring world in the far distant future. Credit: Image by Tushar Mittal using Celestia 2001-2010, Celestia Development Team.

The ring system would last for about 100 Million years, occasionally showering Mars with a stream of meteorites from leftover moon dust.  You may wonder whether something like this will ever happen to Earth’s Moon.  The good news is that it won’t since our Moon is moving away from Earth a few centimeters each year, while Phobos moves toward Mars a few centimeters each year.  The worst thing this means for future humans is that we won’t be able to see a total solar eclipse.

Looking at the distant past and far future is not due to some phony psychic thing.  It’s not reading an ancient book or going by predictions from someone claiming to have powers beyond the rest of us.  It’s science, a verb.  A process by which we can look at evidence throughout our world, our solar system, and our universe to reach conclusions about how things once happened, how they are happening now, and how they will happen in the future.  It doesn’t have all the answers, but it sure does make for an amazing adventure to discover truth.



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