Amateur astronomers are puzzling over a seemingly anomalous cloud that has shown up on images of Mars taken over the past few days. Is it really a cloud, or a trick of the eye? Does it really extend 150 miles up from the surface, as some of the observers suggest? And what churned up all that stuff, anyway? The amateurs and the pros will be trying to resolve those questions before the phenomenon fades away.
"It's not completely unexpected," Jonathon Hill, a member of the team at the Mars Space Flight Facility at Arizona State University, told me today. "But it's bigger than we would expect, and it's definitely something that our atmosphere guys want to take a look at."
Hill and his colleagues will be looking at the area where the cloud was spotted using the Thermal Emission Imaging System, or THEMIS, which is one of the instruments on NASA's Mars Odyssey orbiter.
"In the command upload we're preparing to send today, we've included observations that will hopefully capture some of these recent clouds," Hill wrote in an email. "Our THEMIS camera on Mars Odyssey is capable of acquiring simultaneous visible and thermal infrared images, so our atmospheric researchers are pretty excited about the possibility of not only getting a good look at the cloud structures, but also their temperatures."
THEMIS will be checking out heightened cloud activity around Mars' shield volcanoes as well as around the southern site spotted by the amateurs. Pictures from a camera on NASA's Mars Reconnaissance Orbiter, called the Mars Color Imager, or MARCI, might provide further clues about the southern cloud feature. And amateur astronomers are sending out the alert for observers to keep a close watch on the Red Planet over the coming days.
There's been lots of buzz about the high-altitude cloud on Cloudy Nights and other online discussion forums for skywatchers. Sky & Telescope's Sean Walker says the puff of white was first noticed on March 20 by Wayne Jaeschke, an amateur astrophotographer from Pennsylvania. Since then, other observers have identified the feature in images going back as far as March 12.