Looking in the infrared is not just a cool effect reserved for movies like Predator. Astronomers peer often in this wavelength range to ascertain temperatures of stars and planets. However, temperature is not the only parameter infrared observations provide. Recent infrared observations of Earth’s sister planet Venus, has led to a surprising discovery – Venus’ spin has slowed.
With the VIRTIS instrument, scientists were able to peer through the shroud of clouds encircling Venus and get a good look at its surface features. What they found was some of the identifiable surface features were not where they should be.
According to data taken from NASA’s Magellan orbiter in the early 1990’s, a day on Venus was equal to 243.0185 Earth days. When scientists observed maps of the planet’s surface taken from VIRTIS and aligned them with photos taken from Magellan, the surface features did not match up.
After ruling out any technological or measurement errors, the researchers concluded that Venus’ rotation has slowed by an average 6.5 minutes. It was only after implementing this rotation rate difference that the features on the two maps aligned. Causes are unknown, but researchers suggest slowed rotation could be due to an exchange of angular momentum between Venus and Earth. Another possibility is that decades-long weather storms could effect rotation rate.
For more information you may read the press release.