An interview with Ray Arvidson

If you’re a faithful follower of the MER mission – and planetary exploration in general – you’ll have seen the title of this post, recognised the name, and smiled, thinking to yourself “Great!” If you’re not…and didn’t… then this latest post is an interview with one of the senior scientists involved in the Mars Exploration Rover mission.

Why?

Well, as regular readers will know, I like to keep this blog quite light and breezy, very much a “beginners blog” for people who want to follow what Oppy is doing, see what she’s seeing, and take part in her epic trek to Endeavour crater. But sometimes my list of “I wonder…” scientific questions gets too long to ignore, and then it’s time to ask someone In The Know. This usually takes the form of me emailing someone on the MER team and cheekily asking them to answer a few questions.

Now, these are very busy, very pressured people, with huge responsibilities and commitments – oh, you know, like driving a multi billion dollar rover on Mars! – but so far no-one I’ve approached has ever ignored my request, or turned me down. I’m always delighted when they write me back, but never surprised, because all the NASA people I’ve met, or had dealings with, have been incredibly generous with their time, and have gladly shared their knowledge with enthusiasm and passion. If that sounds a bit gushy, well, I make no apologies for that. They deserve the credit.

So… with lots of questions in my mind about what Oppy has done recently, and what she will do in the future, I decided to email the Deputy Principal Investigator for the Mars Exploration Rover Mission, Ray Arvidson, and just ask them. He emailed me back right away, and was more than happy to answer my questions, for which I am extremely grateful. I learned a lot from his answers, and I’m sure you will, too.

And a very special “Thank you!” to AJS Rayl for helping me set this up! 🙂

Firstly, thanks for agreeing to talk to “Road to Endeavour”, especially when you’re so busy. Before we move on to the questions, would you mind telling RtE’s readers what your role within the MER team and mission is?

I am the Deputy Principal Investigator for the Mars Exploration Rover Mission.  My duties include chairing many of the Science Operations Working Group Meetings, making sure we have a strategic plan, organizing special issues of the Journal of Geophysical Research for MER papers, writing overview papers that present mission results and scientific highlights. I also work with the rover planners on mobility issues focused on terramechanics, the interaction of the rovers with soils and associated wheel sinkage and slip. My lab runs the NASA Planetary Data System Geosciences Node and we archive most of the MER data (http://pds-geosciences.wustl.edu/). I coordinate orbital and rover-based observations, particularly with respect to OMEGA and CRISM, since I am a Co-Investigator for both of those instruments.

You’ve been involved in all the major Mars missions of the past 20 years, so the Red Planet obviously has a special place in your heart. How old were you when you “discovered” Mars? What triggered your interest in it?

I have been involved in mission operations and science analysis for the Viking Landers, Mars Global Surveyor, Odyssey, Mars Express (OMEGA), MER, and MRO (CRISM). I also was involved in the Magellan Mission to Venus. I started graduate school in 1969, just when planetary sciences began as a robust discipline. I did it because I want to explore frontiers, perhaps oceans, perhaps space. I chose space. I was 21.

The MER mission has both revolutionised our view of Mars, and inspired a whole generation of people. Had you any idea, back on Spirit’s landing day, that the rovers would be so successful and become so iconic?

I suspected that the MERs would revolutionize our understanding of Mars when Steve and I started planning the missions and writing proposals. I never in my most positive moments thought we would still be sequencing operations for even one of the rovers in May 2011 or that Opportunity would travel over 28 km. We have had a superb group of engineers and scientists together since the very beginning of MER, and coupled with well built vehicles and instruments, we have been able to make discoveries that have set the “bar” for surface missions very high indeed.

Are you and the MER team aware of the level of fascination with the Mars Exploration Rovers “out here” amongst the space enthusiast community, i.e. all the blogs, forums and websites covering their every move? How does it feel to be part of such a well-loved mission?

We are aware of the high level of interest for MER in the public’s mind. We very much appreciate it and work very hard to get interesting results out to the public and science community as soon as possible. It still amazes me to speak to people I randomly encounter during travels who know about the rovers and some even ask why we did a particular measurement campaign or drove to a particular target. I still love to go to work to see what Opportunity has done and then plan its next set of operations. For example, tomorrow.

It must be a very bitter-sweet time for the MER team, celebrating Oppy’s continuing success as she steams on towards Endeavour while waiting for a signal from Spirit, which has been silent for so long now. How do you stop the team from dwelling too much on Spirit’s fate? Everyone involved in the mission knew from the start that the day would come when one of the rovers became the first to stop working, but it must still be hard to accept after so long..?

Both Spirit and Opportunity have performed beyond expectations. We are all sad to not have heard from Spirit. On the other hand it is amazing that we are only ~4+ km from Endeavour’s rim with Opportunity. We are realistic about expectations since these vehicles are so far “out of warranty” that we consider ourselves fortunate to have one of the vehicles approaching yet another new terrain (the ancient or Noachian rim of Endeavour crater with Fe/Mg smectites exposed) and when we get there we will have a new set of mission objectives that will focus on validating the presence of these clay minerals and inferring their environment of deposition.

Santa Maria looked pretty average and unimpressive from orbit, on the HiRISE photos, but obviously, from the amount of time Opportunity spent there, it was a fascinating scientific site. Can you tell us how scientifically rewarding Santa Maria was in the end?

Santa Maria crater is about 100 m across and relatively young. It was on the path to Endeavour and we encountered it about the time Opportunity needed to stop for a couple of weeks for solar conjunction. Thus the timing was right to explore a young and relatively fresh impact crater. Lots of stereo and color imaging data were acquired. In addition we used CRISM in a new way, dwelling on Santa Maria and oversampling the number of pixels (18 m across) for this relatively small target. This was possible by new commands for the gimbaled platform that rotates the optics. This oversampling produced a kind of super resolution view of the crater and allowed retrieval of spectral reflectances for areas smaller than 18 m across. The SE rim showed spectral evidence of a mono-hydrated sulfate, most likely kieserite. Oversampling observations recently acquired of Victoria crater also show this unique spectral signature. So, we drove Opportunity to the pixels on the SE rim of Santa Maria crater and made detailed MI, MB, APXS measurements, with long duration MB over solar conjunction. The idea was to develop a self-consistent model of the mineralogy for these interesting rim rocks. This is work in progress but kieserite seems to be the winner based on all the measurements. This mono-hydrated sulfate provides information on past environmental conditions that we are working out as I write this summary.

With its hills growing larger and clearer on the horizon every day, Endeavour seems close enough to touch now. Can you give a few more details about the plans for Oppy’s “landfall” at Cape York? I understand she’s going to approach Cape York from Botany Bay, to the south? Will she then drive up onto Cape York to study the crater and its ejecta at the southern end, or head on up to the higher ground further north first?

Opportunity will cross Botany Bay and make measurements of the exposed plains rocks because newly acquired oversampled CRISM observations indicate the presence of poly-hydrated sulfate mineral exposures that we wish to check out. We will then access the Fe/Mg smectites on the Endeavour side of Cape York (ancient Endeavour rim materials) to make detailed measurements. We are working on using CRISM oversampled data to show in detail the pixel locations with the smectite signatures and also the best way to approach these outcrops, given that they tilt toward Endeavour by about 10 to 15 degrees. 

Every recent press release, interview and Tweet has made it clear that the main appeal of Endeavour is the possibility of finding and studying ‘phylosillicates’ there. MSL will be going hunting for these too, whenever and wherever she lands. Could you explain for Road to Endeavour’s readers a) exactly what these are, b) why they’re so important, and c) just how huge a deal it would be if Oppy got to study them at Endeavour?

The various hydrated mineral signatures provide evidence for varying environments of deposition and we are using CRISM data to direct Opportunity to check out these areas (sulfates and smectites) and make detailed ground truth measurements. Sulfates probably formed in ancient ephemeral lakes under oxidizing conditions as Mars was drying out whereas the smectites may have formed in a wetter, less oxidizing environment. Maybe by surface weathering of Endeavour before the crater was largely buried by the younger sulfate deposits.

There are several different charts, on different PDF publications, showing CRISM views of Cape York and the hills to the south. It’s a little confusing! Can you clarify which are the most promising sites for finding those phylosillicates? Maybe Opportunity will have to continue on to Tribulation before she can sample them properly?

The new oversampled CRISM data do show with high confidence these outcrops on Cape York. There are larger areal exposures of smectites on Cape Tribulation, but these will be more difficult to get to since they are further away from Opportunity located in-board to Endeavour with slopes of 15 to 20 degrees. The confusion you mention is because the original detections were from CRISM normally-sampled data and maybe or maybe do not show smectites on Cape York. The new oversampled CRISM data leave no doubt about their presence on Cape York.

All these years… so many kilometres driven… so many thousands of images taken… Almost impossible to choose, I know, but have you one image (or maybe a couple!) that, for you, really capture the spirit and success of the MER mission?

My favorite image is the last Pancam color mosaic we acquired for Spirit after the vehicle drove backwards about ~39 cm using the “breast stroke” technique of rotating the wheels and driving backwards and repeating the operation. This broke the vehicle free of its embedding and we were on the way out of Troy before we stopped to prepare the rover for winter. This mosaic also exposed more of the sulfate sands in Scamander. 

And finally, in years to come, when both Spirit and Opportunity have ended their missions, and stand silently on Mars, half-buried by dust, what do you think the legacy of the MER mission will be? It’s hard to imagine any subsequent mission – short of an actual manned landing on Mars – capturing the public’s imagination so much.

Our legacy? You get what you pay for. MER was not a cheap mission. The vehicles were well-designed and built and were tested thoroughly. On the other hand the science benefit/cost ratio has been outstanding. I do suspect that Curiosity may outpace MER in interest and increase in scientific knowledge, but let’s wait and see.

Thank you VERY much for taking the time to talk to “Road to Endeavour”.

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If you’d like to know more about Ray, you can find a detailed biog here: http://eps.wustl.edu/people/Raymond_Arvidson