Mars Rover Finds Unusual Rocks at 'Home Plate'

An anonymous reader writes "After several months of driving nearly a kilometer, the Mars Rover Spirit has reached the semicircular plateau dubbed 'Home Plate' in Gusev Crater and has unearthed a puzzle. Spirit first got a good view of Home Plate in late August from 'Husband Hill'. The layered appearance is unlike anything yet seen by the rovers."

In all fairness

[edremy]

If you read Squyres' book, he knew that 90 days was totally doable, but wasn't sure about much longer. The original plan was for 30 days, but he figured they couldn't get any science at all in that short a time and they needed funding for at least 90. Dust buildup on the solar panels was going to cripple the rovers quickly since they couldn't figure out a good way to clean the panels.

They never expected the Martians to clean the panels off periodically. (Dust devils, actually) Check out some of the recent photos- the panels are amazingly clean, far better than they ever hoped. Even so, the rovers aren't in good shape- Spirit has no teeth left on the RAT and has several steering motors with issues, Opportunity has major problems with it's robotic arm and how the mini-TES is still working without nighttime heat is unknown.

Re:Sediment?

[Anonymous Coward]

They are sedimentary layers of some kind -- either volcanically deposited (e.g., like an ash fall) or sediment deposited by fluids (air or water). Once they get the instruments up against the outcrop and get some composition data, it should help narrow the possibilities.

The structure looks somewhat like the sediments that have been observed by Opportunity at Meridiani, sans "blueberries" (hematite concretions), though one possible blueberry has turned up (e.g., the far left of this image [nasa.gov]), and there might be more upon closer examination. There are examples of what appears to be cross bedding (cross-cutting laminations indicating ripples or dunes in cross section -- some are visible in the above image), and there are broader vertical composition variations, judging by variations in bedding character and colour.

The cross bedding is especially important, because although there have been examples reported at the Opportunity sites, they aren't 100% convincing. The ones here already look unambiguous. Furthermore, the geometry of cross beds is specific to the current/wave regime and the nature of the fluid carrying the sediment. They can still occur in volcanic settings, but either way, they can provide quite a bit of information about the process responsible.

I'm going way out on a ledge here, but ... damn, those cross beds look rather similar to something geologists on Earth call "hummocky cross stratification" (or HCS for short). It is characteristic of combined flow -- oscillatory and unidirectional -- which is in turn characteristic of storm waves in oceans or large lakes, though the process by which HCS forms is not very well understood. The crossbeds don't look particularly aeolian (wind-deposited).

Unfortunately, I suspect such an interpretation would be much more debatable on Mars. I'm not sure what effect lower gravity and different atmospheric density has on the types of cross bedding that forms. I think there is some experimental and computational modelling for Martian conditions, but I'm not familiar with it.

Still, the deposit certainly isn't a lava flow.

My guess: it is a sedimentary deposit, and I'm also guessing it is stratigraphically above what is found on most of the Gusev plain. It might represent a relict that used to fill much of the basin and lapped onto the Columbia Hills, but has been eroded away over most of the surrounding area. If so, "Home Plate" might be the "lake deposits" people were expecting to find at Gusev from the start.

For a geologist this outcrop is very exciting stuff. And to think that if the rovers only met their standard 90-day lifetime, we would never have seen it!

Re:Late Breaking News:

[Spy der Mann]

Google for it [google.com] :)

Re:Keeps going, and going, and going...

[vsprintf]

Instead, they said the rovers had a 3 month life expectancy, and everyone is slapping Nasa on the back after 2 years into the mission. I think Nasa purposely make the 3 months comment just to reap the benefits of finally having a successful mission to mars.

Then you would be wrong. The 3-month designed life expectancy is the period it takes to accomplish the mission's primary goals. If the primary goals are accomplished, the mission is a success, if not it is considered a failure. Anything after that is gravy. Generally, mission operations are initially approved/funded only for the designed life expectancy, and any operations after that requires additional approval and funding. Try to remember that the satellite in space or a rover on another planet is only a part of a mission's costs.

Barring any significant dust or wind storms, there is no reason why the rovers should not have lasted this long if they are solar powered and reasonably well engineered.

Stuff happens. Like when they unexpectedly found what appeared to be saline mud under the rover wheels that certainly weren't designed for it. Supposedly, the Titanic was "reasonably well engineered", and we had far more experience with ship building at the time than we do now with building semi-autonomous exploration vehicles for other planets.

What is unbelievable is that Nasa designed something that didn't f*ck up in the first 3 months, or even on landing.

Over twenty years ago, NASA launched a satellite with a 3-year mission. There have been 13 points of failure, but thanks to built in redundancy, some clever engineers, and the ability to reprogram (for lack of a better term) the craft, it is still doing its job. Some years back NASA sent up a satellite with an experimental sensor and a 1-year maximum mission. Due to scientific interest in the data being returned, it is still flying after more than 5 years although it is out of fuel. First, you claim NASA over-engineered the rovers and then claim that NASA can't engineer anything in the first place.

Your car would last a century if some company put 800+ million into creating it, I would expect the same from a couple of 400 million dollar platforms with wheels on them.

The actual cost of the vehicle is a small part of the mission cost. The satellite I just mentioned was built for under $500,000, while the cost of the mission has been much greater. Royal Caribbean is building a cruise ship for over a billion dollars. Even with people to service and repair it, I doubt it will still be sailing cruises in 100 years (and that doesn't include operations costs as long as we're comparing cruise ships to Mars rovers).

Re:Define issues with steering motors

[edremy]

They're having fits. Since the rovers can steer every wheel this can be overcome. (Ditto 6 wheel drive: when they started losing a front wheel drive motor when climbing Husband Hill they were able to drive in reverse using only 5 drive wheels and dragging the other.) See for example the February 6 update on Spirit

Spirit completed two diagnostic tests of the dynamic brakes on sol 735 (Jan. 27, 2006) after the team detected a dynamic brake fault associated with the left-front and right-rear steering actuators on Sol 733. The tests were copies of tests that were run after a similar anomaly on sol 265 for Spirit. Also on sol 735, the rover performed a small wheel wiggle after its drive to test the dynamic brakes. The wheel wiggle steered the wheels slightly, then steered them straight. No dynamic brake warnings were observed. The intermittent behavior of the relay status that controls the dynamic brakes, as well as the results of the diagnostic activities, are consistent with the behavior observed after the sol 265 anomaly. The team continued with the same resolution, which was to instruct the rover to ignore the dynamic brake error status. Driving has continued with normal steering function.