Another (methane) puzzle piece falls into place

This post is, effectively, a continuation of a previous discussion about methane but with an important added piece of the puzzle included: a solution which includes the constraint levied by the Trace Gas Orbiter. Since it's very hard to draw/visualize methane, this post like so many others, has a wonderful picture of the spacecraft that made the measurements - the curiosity rover, pictured above, with a jigsaw puzzle mask for effect! (original masking image CC 2.0 description and license here)

You might think it a bit strange, publishing two papers back to back 4 months apart on the same topic. After all, my last paper talking about methane on Mars only came out in Nature Geoscience in March and was fully published in May. And now, here my co-authors and I am again with a paper in Geophysical Research Letters talking about explanations for the seasonal cycle. Part of the story has to do with differences in time to publication for the two journals. But the bigger story is that this past year has seen a surprisingly quick evolution in our understanding of this trace gas.

A small step towards solving the mystery of martian methane

What does the seasonal cycle detected in Curiosity's record of methane concentration mean? Last week, I published a paper in Nature Geoscience with eight of my colleagues that attempts to answer that question. In the spirit of what I put together for my Nature penitentes paper back in January of 2017, I've decided to summarize the work here. This work was three years in the making, but the story of how it came to pass is much less exciting than with the penitentes - simply a combination of hard work and tenacity by my colleagues and I, like all good science. You can't tell the story of my paper without knowing the story of Martian Methane. So I've put together a primer. For those of you who have been following this closely, skip down to Chapter 2.

Chapter 1: The methane story so far

Whither methane, Mars' most mysterious gas? Since it was first discovered telescopically by Michael Mumma's group in 2003, methane has captivated our interest in the red planet. And with good reason: on the Earth, most methane is produced by biology.

Could the same be true on Mars? That's a complicated question to answer. For starters, there's very little of the stuff to go around. On Earth, methane makes up just under 2 parts per million (ppmv*) of the atmosphere, whereas on Mars the values recorded by different groups place the value at between 0.5 and 50 parts per billion (ppbv*) of the much thinner atmosphere. That allows other processes to have a significant effect. For instance, serpentinization of rocks at depth can also produce enough methane to explain these values, as can seeps of methane stored during Mars' early history either as organic carbon compounds or in methane clathrates. Heck, there's even enough accretion of organic matter via Interplanetary Dust Particles each year to produce 11 ppbv if it all gets converted into methane! None of this even considers processes that remove methane from the atmosphere.

An Updated Model for Methane

The gorgeous view from the Utah Valley Convention Center in Provo. Today I'm talking about what I'm not presenting here (a project conceived, executed, written up, submitted, reviewed and accepted all after the deadline for DPS abstracts!)

Greetings from the 49th annual meeting of the American Astronomical Society's Division for Planetary Sciences! While a bit on the colder side, it's a gloriously sunny day here in Provo, Utah.
But I'm not here to talk about the conference. I've already submitted my talk and picked up my poster, so I've got a few minutes before the reception starts to catch up on my writing a little.

Instead, I wanted to spend some digital ink on my 50th paper (18th 1st author paper) which just came out in-press at Planetary and Space Science. While that's a milestone worth some commentary, I'd like to focus in this post on the Science itself. This particular paper is a novel one for me in that it is an update of a previous model that I had created back in 2012. In fact, a perceptive reader will notice some parallels between this paper and that of Moores and Schuerger (2012). Those are intentional. Indeed, it was our express intention to re-examine our earlier results in light of just how far research on martian methane has come over the past five years.