Mysterious Spot found on Venus

(Illustration: Melillo/Maxson/ESA/University of Wisconsin-Madison/ALPO)

A new, bright spot in the clouds of Venus was reported by amateur astronomer Frank Melillo on 19 July

Observations show that the spot had already spread out somewhat by the end of last week, and astronomers are awaiting more recent observations from Venus Express.

The spot is bright at ultraviolet wavelengths, which may argue against a meteoroid impact as a cause. That's because rocky bodies, with the exception of objects very rich in water ice, should cause an impact site to darken at ultraviolet wavelengths as it fills with debris that absorbs such light, says Sanjay Limaye of the University of Wisconsin-Madison and a member of the Venus Express team.

Powerful eruption?

Another possibility is that a gust of charged particles from the sun could have created the glow by energising a patch of the upper atmosphere. Alternatively, waves in the atmosphere, which trigger turbulence and are thought to carry material up and down, could have concentrated bright material to create the spot.

A volcanic eruption is another suspect. Venus boasts the most volcanoes of any planet in the solar system, and nearly 90% of its surface is covered by basaltic lava flows, although no 'smoking gun' has yet been found for current volcanic activity. But an eruption would have had to be very powerful to punch through a dense layer in Venus's atmosphere to create the spot some 65 to 70 kilometres above the planet's surface.

"It's fair to say something unusual happened on Venus. Unfortunately, we don't know what happened," Limaye