What is this cloudy spot on Mars?

Mars watchers have a bit of a mystery on their hands. An astronomy buff captured this photo of the red planet, with what looks like a growth emerging from the sphere. So is it a towering cloud? Or just a trick of the light?

Amateur astronomer Wayne Jaeschke has taken many pictures of the night sky, but when he took this photo of Mars, he knew it was something unusual. He posted the photo on the site Cloudy Nights, explaining that sources had suggested it was a high-altitude water-ice cloud over Mars' Acidalia region.

What is this cloudy spot on Mars?

The Mars Space Flight Facility at Arizona State University has also been observing the curious cloudy spot using the Thermal Emission Imaging System on NASA's Mars Odyssey orbiter. There are still a number of theories as to the origin of the cloud — it could be debris from a meteor impact, a towering weather system, or perhaps just a trick of the light. You can see Jaeschke's animation of the anomaly to get a better sense of what they're looking at.

Whatever it is, the anomaly is shrinking. In the meantime, professional and amateur astronomers are working in tandem to figure out just what's going on out there on Mars.

Mysterious cloud spotted on Mars [Cosmic Log via Metafilter]