Inside Opportunity: South!
As I write this update, we are now perched on the western flanks of Spirit Mound, a rather strange little hill, sitting on the floor of Bitterroot Valley, which is dipping eastward down towards the floor of Endeavour Crater. Presently, Opportunity has her arm down examining a unique light-toned outcrop that we have named Gasconade. Our team is excited and anxiously awaiting the results from the Alpha Particle X-Ray Spectrometer (APXS) which will tell us about the composition of this layer.
Opportunity is driving down this valley as part of our tenth extended mission in search of more of the oldest rocks that contained clay minerals, which we first encountered at Cape York.
Clays are important because they tell us about a time in Mars’ early history when there was abundant water to weather the rocks and form clay minerals. This also tells us about the past water chemistry because clay minerals do not form in acidic water but rather in a neutral ph water (think drinking water).
You may recall that we found evidence for ancient shallow-standing bodies of water early in our mission in 2004, but this water was more like battery acid than what comes out of your tap.
It is now springtime on Mars for where Opportunity is located (this past July 4 was the first day of Spring in the Southern Hemisphere), and we have finally left the familiar confines of Marathon Valley. We explored Marathon Valley for just over a year and on our way out came across some very interesting yet enigmatic grooves carved into the valley floor. We conducted an extensive imaging campaign to document these unusual features before moving on to the south.
Those of us on Opportunity’s science team are not yet sure how these grooves formed, but it appears that wind or water (or both) were the likely agents of erosion. Our work here should help us when we reach a true gully further south along the western rim of Endeavour Crater. This sinuous gully appears to have been fully carved by running water, and upon reaching it, we will become the first team in history to study an ancient Martian waterway up close and personal from the surface.
Upon driving away from the grooves, we next approached the Lewis and Clark Gap, which is an opening between two ridge systems (Knudsen Ridge to the west and Wharton Ridge to the east). This opening should allow us to drive south into the next valley, which we have named Bitterroot.
We crossed the Lewis and Clark Gap into Bitterroot Valley on sol 4484 (Sept. 3) and noticed an immediate and obvious change in the amount of debris on the floor of Bitterroot Valley compared to that on Marathon Valley. The floor here is very ‘dirty’ compared to the relatively clean floor of Marathon Valley. The term ‘dirty’ is one that I used to describe the appearance of the valley floor to fellow team members, and it relates to the amount of rocky debris scattered across the bottom of Bitterroot Valley.
Now a little bit about our naming theme. You may have noticed that, for the past year, we have been using names of members of the Lewis and Clark expedition, also known as the Corps of Discovery.
We have used all these names up now and have moved on to names from locations they visited in their explorations of the American western frontier. We also used some names from the Viking 1 and Viking 2 lander missions, which were the first to successfully land on Mars. We did this to honor the fortieth anniversary of their touching down on the surface of the Red Planet on July 20 and Sept. 3 of 1976.
Opportunity touched down on the surface of Mars back in 2004. Her mission was only slated to last three months. More than eleven years later, we’re still directing her investigations into Mars’ geology, and there is no telling what we will find over the next hill or down in the valley over. We don’t know if she will finally give out in the next few minutes after you read this – but we do know that she has rewritten what we thought we knew about Mars’ history.
Dr. Jim W. Rice, Jr., is an Astrogeologist at the Planetary Science Institute, he has over 25 years research experience specializing on the surface geology and history of water on Mars. Dr. Rice is currently a Co-Investigator and Geology Team Leader on the Mars Exploration Rover Project (Spirit and Opportunity). Rice also has extensive mission experience as Associate Project Scientist on the Lunar Reconnaissance Orbiter and Mars Odyssey Orbiter Projects. He has been involved in Mars landing site selection and certification activities for every NASA Mars Mission since Mars Pathfinder. His career includes working for NASA, Astrogeology Headquarters of the United States Geological Survey, the Mars Spaceflight Facility located at Arizona State University and the Lunar and Planetary Laboratory located at the University of Arizona.