Venus will pass in front of the sun from Earth’s perspective on Tuesday (June 5,
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Wednesday, June 6, in much of the Eastern Hemisphere), marking the last such Venus transit until 2117. However, there’s a chance to observe an Earth transit less than two years from now using a little creative thinking, some researchers note. In January 2014, Jupiter will witness a transit of Earth. And we can see it too, the astronomers say, by training NASA’s Hubble Space Telescope on the huge planet and studying the sunlight it reflects. A transit of Earth would be an unprecedented skywatching spectacle, but the main allure of the event for scientists is the chance to see what the atmosphere of a habitable (and inhabited) world looks like from afar. This information could help astronomers in their search for life on distant alien planets. Hubble is already gearing up for a similar observation of the coming Venus transit. The instrument is too sensitive to be pointed anywhere near the sun, so scientists will use the moon as a mirror. The goal is to see if Hubble can determine the makeup of Venus’ atmosphere, which is well-studied, in a test of how well the technique can be applied to exoplanets. According to Jay Pasachoff, of Williams College watching the Earth transit with Hubble, while challenging, is quite doable. Pasachoff and his colleagues have applied for time on Hubble to watch a September 2012 Venus transit in light reflected off Jupiter, as a sort of proof of principle. They should know by June 15 if their proposal was successful, Pasachoff said. If they are granted Hubble time for the September Venus transit, the researchers will apply to watch the January 2014 Earth transit. The team isn’t taking anything for granted, since Hubble time is so hotly contested. If their bid fails, Hubble likely will never get to see an Earth transit. The next one from Jupiter’s perspective won’t occur until 2026, and the venerable instrument, which launched in 1990, is expected to shut its eyes before then.