Venus Express observing Earth too for signs of life

Venus in the sky just after sunset. Earth is about this size from Venus too.

This is a cool thing you'll see probes doing every once in a while when the opportunity arises, to observe Earth from a distance to see what it looks like from that far out in order to gather data to aid in determining whether Earth-like planets we find in the future will be inhabitable or not.

"When the Earth is in a good position, we observe it two or three times per month," says Giuseppe Piccioni, Venus Express VIRTIS Co-Principal Investigator, at IASF-INAF, Rome, Italy. The instrument has now amassed approximately 40 images of Earth over the last two years.

The images of Earth cover both visible and near-infrared regions of the spectrum and can be split into spectra, in order to search for the signature of molecules in the Earth's atmosphere.

The value of the images lies in the fact that Earth spans less than a pixel in Venus Express's cameras. In other words, it appears as a single dot with no visible surface details. This situation is something that astronomers expect to soon face in their quest for Earth-sized worlds around other stars.

"We want to know what can we discern about the Earth's habitability based on such observations. Whatever we learn about Earth, we can then apply to the study of other worlds," says Grinspoon.

Since 1995, astronomers have been discovering these extrasolar planets and now know of more than three hundred. As observational techniques have been refined and the data continuously taken, so smaller and smaller planets have been discovered.

Now, with CNES-ESA's COROT and NASA's Kepler missions, the prospect of discovering Earth-sized worlds in Earth-like orbits around other stars is better than ever. "We are now on the verge of finding Earth-like planets," says Grinspoon.

and:

The team will also compare spectra of the Earth's oceans with those taken when the continents are facing Venus Express. "We have initiated the first sustained programme of Earth observation from a distant platform," says Grinspoon. Although the observations may not tell us anything new about the Earth, they will allow us to unveil far-off worlds, making them seem more real than simply dots of light.

By the way, the next transit of Venus will be June 2012, and I see that it'll be best observed from East Asia where I live and down to Australia.