May 4, 2012: This mottled landscape showing the impact crater
Tycho is among the most violent-looking places on our Moon.
Astronomers didn't aim NASA's Hubble Space Telescope to study
Tycho, however. The image was taken in preparation to observe
the transit of Venus across the Sun's face on June 5-6. Hubble
cannot look at the Sun directly, so astronomers are planning to
point the telescope at Earth's moon, using it as a mirror to
capture reflected sunlight and isolate the small fraction of the
light that passes through Venus's atmosphere. Imprinted on that
small amount of light are the fingerprints of the planet's
atmospheric makeup. These observations will mimic a technique
that is already being used to sample the atmospheres of giant
planets outside our solar system passing in front of their
stars. In the case of the Venus transit observations,
astronomers already know the chemical makeup of Venus's
atmosphere, and that it does not show signs of life on the
planet. But the Venus transit will be used to test