Ghosts don’t just float around haunted houses. Curiosity recently captured images of phantom clouds above Mars that give us a rare glimpse into its past.
NASA believes the wraithlike ice-crystal clouds, which eerily mirror those on Earth, are “the most clearly visible so far.” They were observed some five degrees south of the equator by the rover’s NavCam as it gazed straight up into the Martian sky and took eight photos and another eight with its camera lowered as they drifted past the planet’s red hills. Then they vanished.
Curiosity team member Charissa Campbell, of York University in Toronto, gave us an even spookier view of the clouds in motion by enhancing the images to really give the frame-by-frame changes emphasis.
“It is likely that the clouds are composed of crystals of water ice that condense out onto dust grains where it is cold in the atmosphere,” said Campbell’s colleague John Moores. “The wisps are created as those crystals fall and evaporate in patterns known as ‘fall streaks’ or ‘mare’s tails.’ While the rover does not have a way to ascertain the altitude of these clouds, on Earth such clouds form at high altitude.”
Mars may have dried up into a dusty frozen wasteland, but if you were around about 3.2 billion years ago, before brutal solar winds stripped it of its atmosphere and any water that might have been, you might have been able to watch wispy clouds drift by lazily, as they do on summer days here on Earth. It is thought that the ancient Martian climate was warm enough for liquid water to flow on the surface. As on our planet, this water would have evaporated and condensed into clouds until it rained down again. They also provided insulation.
“Mars could have been kept warm by global cirrus cloud decks,” said scientists Ramses Ramirez and James Kasting from the Carl Sagan Institute in a study published in Icarus last year, further suggesting that they occurred often on the Red Planet and hold for up to five times longer than Earth clouds. “Initial warming from some other process, e.g., impacts, would be required to make this model work.”
The study also found that under certain conditions, the clouds could have raised global temperatures on Mars above freezing.
Hauntings on Earth may be more common than clouds on Mars today, but at least we’ve been able to peer into the distant past through Curiosity’s lens.