In July 2015 NASA’s sun-monitoring spacecraft STEREO-A was almost exactly behind the sun from Earth’s perspective – so it could not communicate with scientists on Earth. This meant that there were no images of the back of the sun available which could have been used to track the movement of sunspots. To overcome this problem, and since there was temporarily no other resource available to provide a view of the sun from the opposite side of the solar system from Earth, NASA’s Curiosity Mars rover’s Mast camera (Mastcam) was turned up to look for sunspots on the face of the sun which was not visible from Earth. Large sunspots were evident in views from Curiosity‘s Mastcam. The sun completes a rotation about once a month – faster near its equator than near its poles. Information about sunspots which develop before they rotate into view of Earth and Earth-orbiting spacecraft is helpful in predicting space-weather effects of solar emissions related to sunspots. Curiosity had been busy investigating bedrock types on Mars’ Mount Sharp and preparing for a drill test at the time.
Large sunspots were evident in views from Curiosity‘s Mast camera. There was temporarily no other resource providing views of the sun from the opposite side of the solar system from Earth.
The main purpose for most imaging of the sun by Curiosity and other Mars rovers has been to monitor how its apparent brightness is affected by dust in Mars’ atmosphere above the rovers. Mark Lemmon of Texas A&M University, College Station, is a Mastcam team member who studies the Martian atmosphere. Three months previously he coordinated sunset imaging by Curiosity for a Martian evening when Mercury was passing directly in front of the sun from Mars’ viewpoint.
“We saw sunspots in the images during the Mercury transit, and I was trying to distinguish Mercury from a sunspot,” Lemmon said. “I checked with heliophysicists who study sunspots and learned that STEREO-A was out of communications, so there was no current information about sunspots on that side of the sun. That’s how we learned it would be useful for Curiosity to monitor sunspots.”
In addition to its sunspot viewing, Curiosity is examining rocks near “Marias Pass.” A test is planned this month for the percussion mechanism of the rover’s sample-collecting drill, which exhibited a transient short circuit during transfer of sample material collected four months ago. The test is designed to provide diagnostic information for use in planning the rover’s next drilling operation, possibly in the Marias Pass area.
Curiosity has been working on Mars since early August 2012. It reached the base of Mount Sharp last year after fruitfully investigating outcrops closer to its landing site and then trekking to the mountain. The main mission objective now is to examine successively higher layers of Mount Sharp.