For space watchers, Mars is like a second home. Astronomers have been studying the Red Planet for centuries – the first map of the Martian surface was sketched 500 years ago. Since then, it has become the most surveyed planet in the solar system, besides Earth. We have sent over 50 robot explorers to patrol its surface and watch it from orbit, seven of which are operational on and around the Red Planet right this minute. It's not for nothing that space aficionados quip that Mars is the only planet known to be inhabited solely by robots.
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.
Nearly three years later, the sighting still defies explanation. In an attempt to pin down the blobs' origins, Agustin Sánchez-Lavega of the University of the Basque Country, Spain, and colleagues, including Peach, sought out images of Mars from that period. They wound up collecting pictures from 18 observers equipped with a variety of small telescopes. The team also searched through old images taken by the Hubble Space Telescope and identified a similar object in 1997.
I would not expect to hear the truth about the phenomenon any time soon. To read more, click here.