NewScientist (paywall) summarizes a Nature article (another paywall) concerning a new mystery of Mars:
So it was that much more surprising when, on 12 March 2012, amateur astronomers around the world noticed a strange blob rising out of the planet’s southern hemisphere, soaring to 250 kilometres above the surface.
They watched for 11 days as it grew to around 1000 kilometres across, even stretching a “finger” out into space. “I was really quite amazed that it was sticking out the side of the planet quite prominently,” says Damian Peach, who lives in Selsey, UK, and was one of the first to spot it.
Poor weather and other issues meant no one had their eye on Mars the following week, and by 2 April it seemed to have disappeared. Then on 6 April a second object of the same type emerged from the same spot and lasted another 10 days. It, too, has not been seen since.
No one has a clue, which makes this quite tantalizing. For comparison, 100 KM altitude is considered to be the edge of space on Earth.
