Gravity Assist Podcast: Mars, Part 2, with Michael Meyer
The Gravity Assist Podcast is hosted by NASA’s Director of Planetary Science, Jim Green, who each week talks to some of the greatest planetary scientists on the planet, giving a guided tour through the Solar System and beyond in the process. This week, he is joined by the “man about Mars,” Bruce Jakosky from the University of Colorado, who is the principal investigator of NASA’s MAVEN mission, and Michael Meyer, NASA’s lead Mars scientist.
Here’s short teaser for Part 2:
Jim Green: Now that we’ve figured out how Mars lost its atmosphere with MAVEN, we can now talk about a couple of other Mars mysteries with Michael Meyer, our lead Mars scientist at NASA Headquarters. I’m really intrigued by some of the recent measurements of methane on Mars. Michael, what’s going on?
Michael Meyer: As you might remember, a couple years ago, when we first started doing the methane measurements, there was all of a sudden – boom – this big spike in methane. And then, almost as surprising, it disappeared. You have to go through chemical gymnastics to get methane to show up and get methane to disappear. The atmospheric modelers are just in a tizzy over this because [we don’t know] how is this possible?
Usually there is a low background of methane, which is fine because you can expect inputs from comet material to give us some methane. But then we found another spike and then [that spike] disappeared. We’re not getting any correlation with anything else that’s going on [on Mars] as we’re exploring. So, this is a real mystery, and it is important because it could be a sign of geological processes where rock is interacting with water, where if you can pick the right rock, you get methane generated, and that would be an active geologic process going on, which would be really interesting.
[But on Earth], most of the methane that we see is a biological product. So, of course, that would obviously be very exciting on Mars, too. Either way, it’s a mystery that needs to be solved because we have to figure out what the source is.
Jim Green: One of the more spectacular sets of observations that the Mars Reconnaissance Orbiter has been making are of the recurring slope lineae (RSL), and there’s been some observations in and around Gale Crater that seem to indicate streaks coming down Mount Sharp, where the Curiosity rover is exploring. What’s our current thinking about those?
Michael Meyer: Yeah, so recurring slope lineae – it’s a mouthful for basically something that shows up seasonally. In the spring when it starts warming up, they appear. Through the summer, they get longer down a slope. In the fall, they start to disappear. In the winter, they’re gone. And the next year, it happens again, and it happens in the same places, and it looks like water flowing down slopes. But, it’s hard to explain that being water just because the temperatures are that low, there isn’t that much [liquid] water on the surface of Mars at all because water’s not stable on the surface. What’s going on?
So, yeah, there have been a couple of candidate recurring slope lineae in Gale Crater, but they’re not very good. I think we only have one or two where the jury’s still out that they might be. But, we’re finding them all around the [rest of the] planet. Mars Reconnaissance Orbiter has been doing a fantastic job of looking at the surface of Mars and seeing change. It’s only because [the spacecraft has] been there for a while that it can see the seasonal progression and digression of each of these things.
One of the challenges and why they’re still a mystery is when we’re looking at the colors of these things to tell what the mineralogy is and what rocks there are, whether or not there’s water there, our spectrometers are not really large enough to get a good spectra. So, we don’t see a real change in the spectra over the seasons. [The RSL] go dark, they go light, and what’s going on because you don’t see it with our other instruments. But, we know it’s real. We know that something’s happening and we don’t have a good explanation yet.
Jim Green: I think we’ve got to get up close and personal, really, to understand what’s going on. So, I think that’s in our future. We’ve got to go visit an RSL.
Michael Meyer: Well, certainly, for the candidate ones that we’ve been talking about in Gale Crater, we have marked out observation posts. So, there’s spots as the Curiosity rover goes along. Way in the distance, it could see the candidate RSL and will image them, at high resolution, plus it has spectrometers. So we can get a different look at [the RSL]. Curiosity can look at it over better periods of time because the Mars Reconnaissance Orbiter can only see the RSL when it passes overhead. So, we have high hopes that, as we go along over the next year and we have these observation posts, we can watch [the RSL] and see whether or not this it is real, or is this like a shadow that shows up and disappears, or is it really something that’s happening on the surface. And then because we can look at it with multi-colored eyes, we can get a better handle on what actually is the cause of the mechanism.
Jim Green: Curiosity’s been doing fantastic and it’s really being a pioneer, telling us that there are regions on Mars that could have been habitable in the past. That means the next mission, which right now we are calling ‘Mars 2020’, is going to have an opportunity to go to those places that Curiosity is uncovering for us that will enable that mission to make even greater progress. So, what’s happening with Mars 2020?
Michael Meyer: You said it very well. I mean, Mars 2020 is really standing on the shoulders of Curiosity in a couple of different ways. One, it’s using the whole architecture of the mission, including the entry, descent and landing, and the rover body itself that has worked so well that we’re doing it again. We’re adding brand new instruments, we’re updating everything and it’s going to cache samples, so that when it finds interesting rocks, we have the opportunity to bring them back.
The other way in which Mars 2020 is standing on the shoulders of Curiosity is that what Curiosity has learned has told us that Mars was habitable during the period of time that Gale Crater was formed, or soon after that. Some of the things about the mineralogy and the rocks tell us what the environment was like. So the instruments that we’re sending on Mars 2020 are informed by that, and then picking the landing site for Mars 2020 is informed by what we’ve learned in Gale Crater and from information we got from orbit, so that when have much more sophisticated thinking about where we should go to get the right rocks that are going to tell us something about the early history of Mars during the period of time that life started on Earth, that life started in our Solar System.
Jim Green: We all get into this field in various ways. It’s just fascinating to me to see how we just turn our attention to space. What was that “gravity assist” that pulled you into this science?
Michael Meyer: You know, it’s a pretty tortuous route from me getting interested in science and actually ending up in the Mars program. I would say the first thing that really got me was that I’d been a fan of Jacques Cousteau, I liked the oceans, I had an aquarium. You know, I was interested in that. I liked to sail, I liked being on the water. Everybody likes being on the water. Then I got hired as a deckhand with a treasure salvaging operation off the coast of Florida. That, in and of itself, was pretty cool. The big thing was, after I was there for a couple of weeks, the head of the operation fired all the divers because they were just not doing the job. And so he asked me if I wanted to dive. Sure, I don’t know how to dive, but I’d be happy to. So I got my opportunity to go scuba diving and help with the treasure salvaging.
There it was, my first foray into the subsurface, and I looked at this world, and despite all the TV shows I’d seen and the occasional book, I looked at this and I went, “My word, I don’t know anything about this world. This is fantastic. Look at all this stuff.” I was just blown away by how fantastic it was, even though I thought I knew a lot about the oceans.
That set me on the track of knowing I could do this for the rest of my life. Now, how I got to Mars is a whole different story, but [the oceans] got me interested in science and looking ahead beyond just going to college, to graduate school and realizing that I could actually make a living by learning things. It was great.
Jim Green: Thanks, Michael. Join us next time as we continue our virtual tour of the solar system. I’m Jim Green, and this is your gravity assist.