It’s been a busy month for Curiosity since last month’s column, with some great news and a few problems. First, the great news.
Curiosity’s main objective is to determine whether Mars could have supported a habitable environment in the past. On Tuesday NASA released the initial results of the analysis of the rock powder from the hole drilled Feb. 8, and the answer is: yes, we have found a location on Mars that was once a habitable environment.
The two main instruments used for this analysis are the Chemistry and Mineralogy and the Sample Analysis at Mars. Using these instruments, scientists identified sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon; on Earth, these are most of the key elements needed for life.
The data also indicates the rover is in an area on Mars that was once at the end of an ancient river system that descended from the rim of Gale Crater. The fine-grained mudstone that the hole was drilled into is made up of at least 20 percent clay minerals; layers in the clay are evidence of multiple periods of wet conditions in the past. Therefore, this area may also have been intermittently a wet lakebed.
But water alone does not make a habitable environment. The Opportunity rover had found signs of water at Meridiani Planum back in 2004, but the rocks at Meridiani contained magnesium and iron sulfates, salts that indicate an environment too acidic for most life. Meridiani also had very little water, so what little was present would have contained very high levels of salts that would have sucked all the fluids out of any potential life forms.
On the other hand, the rocks at Gale Crater contain calcium sulfate and halite, which form in a more neutral environment. The clay minerals that were found in the sample are also a product of fresh water and igneous minerals.
John Grotzinger, lead scientist for the Mars Science Laboratory mission, said, “We have found a habitable environment that is so benign and is so supportive of life that probably if this water was around and you had been on the planet, you would have been able to drink it.”
Another important discovery was that the powder from the drilling was gray, not red like most of the surface soil. It had been hoped that material inside the rocks would be protected from the surface radiation that oxidizes the iron and turns it red.
The gray color indicates that much of the sample contains less oxidized forms that are more conducive to life. Analysis found a mixture of oxidized, less-oxidized, and even non-oxidized chemicals. Non-oxidized forms are an energy source for some microbes on Earth.
And now, the problems.
On Feb. 27, during a scheduled communication window, Curiosity did not send recorded data as expected, only current status information. The status information revealed the computer had not switched to its usual daily sleep mode. Test simulations at JPL indicated the cause to be corrupted memory being used by the A-side computer. Curiosity carries a pair of redundant main computers to have a backup; these are known as A-side and B-side computers.
The next day, ground controllers switched from the A-side computer to the B-side. This automatically puts the rover into safe mode, in which only minimal activities are carried out. Science work is put on hold. Controllers are continuing to work to restore A-side as a viable backup.
The transition from safe mode back to operational mode on the new computer takes several days to complete. On March 2, Curiosity came out of safe mode, and it was hoped science operations could restart as soon as the following weekend.
But on March 5, the sun unleashed a medium-strength flare. Curiosity is designed to handle the increased radiation this type of flare creates on the surface of Mars. But as a precaution, controllers put Curiosity back into safe mode until the storm passed.
The next problem will occur for about two weeks centered on April 18, when we will not have reliable communications with Curiosity because of solar conjunction. Solar conjunction means that from Earth, Mars appears to be behind the Sun. Thus, the Sun will interfere with most of the radio signals sent to Mars.
To deal with this problem, controllers will turn off some instruments and will send two weeks of instructions to Curiosity prior to conjunction. Normal operations should resume by the first of May.
What about those science instruments I had promised to explain this month? With all this other news, that will have to wait until next month, when Curiosity will be on its own.
Marty Scott is the astronomy instructor at Walla Walla University, and also builds telescopes and works with computer simulations. He can be reached at firstname.lastname@example.org.