I’m always delighted when members of the insanely-busy MER team agree to ‘talk’ to this blog, by answering a selection of emailed questions, and I was especially pleased when NASA’s Dr Barbara Cohen, from the Marshall Spaceflight Centre in Huntsville, recently said she’d be happy to. If you’re on Twitter, and follow the exploration of Mars, you’ll know Dr Cohen better as “@barbylon”, one of the most prolific MER-related Tweeters. If you’re not, then I’m sure you’ve seen her name on scientific papers and seen her name dropped elsewhere. So, for this post we’re going to chat with Dr Cohen (below) all about Mars, the amazing journey of the rovers so far, and what lies ahead…
Thanks for talking to “Road to Endeavour”! Can you tell our readers a little about yourself?
I've been a MER science team member since Spirit sol 660 ish. I love the spacecraft operations side of the project and serve in many roles including Science chair, mineralogy/geochemistry theme group lead, and uplink/downlink for the APXS and Mossbauer instruments. My science interests are in the impact process on planets - how it is recorded in the rocks. So I look at rocks in the lab and in the field and try to figure out when and how they were impacted.
Thanks. I’d like to start by going back in time a little. Oppy is now exploring Endeavour Crater, but before Endeavour there was Victoria. What did you think when Opportunity pulled up at the edge of Victoria and we saw all those beautiful capes, cliffs and rock layers?
Oh, Victoria was beautiful. I loved it because it was a giant crater, but one you could still take in with the view and wrap your mind around, sort of like the scale of Meteor Crater. The bays were certainly a boon for people like me who like impact craters. These were places that cut back into the crater sides and ejecta and gave us the stunning cross-sections we see in the capes.
What did we learn at Victoria? What did driving down the ramp of Duck Bay to study Cape Verde’s layers and rocks tell us?
Impact craters are a natural window into the subsurface. You get to see all the things you’d see in a drill section or core, but the work’s already been done. At Meridiani, the surface materials were pretty constant, so we were going to bigger and bigger craters to try to see what was beneath that Burns Formation sandstone. At Victoria, we saw that the crater walls, and the ejecta that came from deep within the crater, was still the same familiar unit. That helps us understand just how thick the Burns Formation sandstone is.
After Victoria it was a long drive down to Endeavour. To an observer, with its endless fields of rippling dust dunes, that beautifully barren landscape was like driving across Arrakis, but was it frustrating for a geologist like yourself? There wasn’t much to see, perhaps? Was each crater like an oasis for you?
Not frustrating, but perhaps long. We all had our “eyes on the prize” – getting to Endeavour. Matt Golombek did some pretty fantastic work comparing all the little craters along the way to each other to learn about their ages and degradation states. That was an interesting story to watch unfold.
As she drove to Endeavour, Oppy discovered lots of meteorites. Personally I loved each and every one of them, and I was always cheering when a new one appeared up ahead, but I know many of my fellow MER followers considered them a distraction. What did you learn from those meteorites, and why were they important?
That reaction mirrors that within the team as well 🙂 The fact that overall, the meteorites are reasonably similar to those on Earth tells us we understand the meteorite sources fairly well. Since we do have the meteorites on Earth, and understand how they degrade, or weather, we can use that to tell how long they have been exposed to geologic processes on Mars. One odd thing is that we saw a lot more iron meteorites, proportionally, than we do on the Earth. That may be because one single iron meteorite broke up and scattered pieces across Meridiani, or alternatively, may be because the Martian atmosphere allowed denser meteorites to pass through while causing stony meteorites to explode as airbursts.
Now – Endeavour! For months MER followers strained to see its rim peeking over the horizon, and when it started to appear we were very excited! But what was it like for you, and the MER team, as Oppy approached Endeavour and saw it opening up before you?
That was definitely a feeling of accomplishment, that the team’s dedication to driving the rover quickly and safely had paid off by getting there with the ability to do new science.
In very simple terms, what IS Cape York? Why did Oppy make landfall here rather than further south where more significant amounts of clays have been detected from orbit?
Endeavour Crater is really old compared with Meridini Planum, and formed in material that underlies the Burns Formation sandstone. The high points around the crater are remnants of Endeavour’s impact ejecta blanket. It’s been eroded now, so only mounds remain rather than a continuous ring. Cape York was the closes remnant of this high-standing, ancient material to Opportunity’s trek, so the first place it made sense to head for. Clay materials have in fact been detected here too, on the inside (south-sloped) edge of Cape York.
So… we’ve driven up the length of Cape York now… past Odyssey crater, up the Shoemaker Ridge, down from Greeley haven and are now parked at the northern edge. The images being sent back are stunning, but a bit hard for non-geologists to interpret. So, imagine you’ve been beamed to Oppy’s side.. tell us what you’re seeing, describe to us what the different features in the landscape are, and why this is such a special place…
Try thinking of it this way. There’s an ancient, basaltic-crusted Mars landscape made from lava flows. A pretty large meteorite hurtles in and blows out Endeavour crater. Material is blasted out of the crater and settles in a blanket over the surrounding landscape. Perhaps from the heat generated by the impact, or from the heat in early Mars, warm water starts circulating in the subsurface cracks and veins, and it’s pH neutral water. As the water and basalt interact, they form clay minerals (and possibly clement abodes for life!). Lots of time goes by, and the crater rim erodes down, the crater starts to fill in. Some time much later, the planet has turned acidic and water is less plentiful. The area around Endeavour hosts a shallow, seasonal, braided stream complex of acidic waters. These waters lap up against the Endeavour ejecta outcrops at their eastern edge. When that dries up, we have flat-lying Meridiani sandstone sort of gently onlapping the high mounds of ancient Endeavour impact ejecta, which is now Shoemaker Ridge. As Steve Squyres has said, It’s a whole new mission here.
Opportunity will be driving south again soon, towards – and then hopefully up onto – Tribulation. As a geologist, why is Tribulation calling out to the science team so loudly?
Cape Tribulation is where we have seen clay minerals from orbit, using the CRISM instrument. Like I said above, clay minerals indicate a pH-neutral, water-rich environment was on Mars to create them. Nobody has ever investigated clay minerals in situ on Mars before. In fact, that’s one of the main reasons we are sending Curiosity to Gale. But Opportunity’s got a few more months to try to get there first 🙂
Ok, enough about rocks! Let’s look at the more human side of the mission. What’s it like to be a part of this amazing mission? To be a part of this remarkable team that’s lived and breathed Mars for the best part of a decade?
Becoming part of the MER team was one of the best things that has happened to me, both professionally and personally. Working on a mission gets you very close to the data in a way that really forces you to learn about Mars, like it or not. The science team is very open and accepting, so it’s a great forum for forming new ideas and getting feedback as you pursue them. And I discovered a passion in myself for helping work with both scientists and engineers to accomplish a space mission that I’m carrying forward in my career.
How has the team been affected by the huge public interest in and support for the mission? You’ve all made extraordinary efforts to keep everyone feel involved in this chapter of martian exploration, shared everything with us that you can. What’s it been like to see Oppy’s and Spirit’s adventures embraced by bloggers, spaceflight fans and armchair explorers around the world?
The public interest is just amazing. One of our team members used Stephen J. Gould’s criteria to show that Spirit and Opportunity are objectively, measurably “cute” to humans. I think this definitely shows up in cartoons and personifications of the rovers that helps bring them closer to the public. But even in terms of science, it’s very gratifying to me and to the team that the work that we’re doing, using the rovers to understand Mars as a planet, is something that is appreciated and not just seen as an obscure waste of time and money.
You’re a very prolific “Tweeter”, posting messages on Twitter as “@barbylon”. How do you think social media has affected the MER mission since it began?
The MER mission has had great public connections since its beginning, with web pages, activities, and images, plus releasing every image as it comes down. I think social media has given an extra dimension as a window into the minds of the scientist, engineers, and public enthusiasts – when I read something on Twitter that got @marsroverdriver excited, I pay more attention. When I read through unmannedspaceflight.com and see something there that people have picked up on, I’m likely to investigate it further.
Thanks again for talking to Road to Endeavour.