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Mercury Transit Foreshadows Future Planet Hunt
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Dr. Jo Pitesky:
Welcome to NASA’s PlanetQuest Podcast, episode 7. I’m Dr. Jo Pitesky.

(Music: French national anthem.)

French-accented voice: "Cunning Mercury wanted to cross without being seen. It came sooner than anyone had expected! But it could not escape being discovered. I found it and saw it! It happened to nobody before me on 7 November 1631 in the morning."

(Scratching needle sound.)

Pitesky: Hold on just a minute. It might have been a Frenchman, Pierre Gassendi, who first observed the Transit of Mercury.

(Music up: German national anthem.)

But it's thanks to a German astronomer, Johannes Kepler, that Gassendi knew when to look for it.

The next transit of Mercury happens this Wednesday afternoon, November 8, 2006 . But you'll need a telescope with a special filter to see it. Astronomy clubs around the country are preparing to share this unusual sight with their communities. Unless you are an experienced astronomical observer, don't try to observe the Mercury Transit on your own. It is very dangerous to view the sun directly.

The transit of Mercury takes place when the planet comes between the Sun and the Earth. Mercury is seen as a small black dot moving across the face of the Sun. It occurs only about 13 times per century

Appropriately, NASA has named a forthcoming planet-finding mission after Kepler, who discovered the laws of planetary motion four centuries ago.

Here's Jim Fanson, deputy project manager for NASA’s Kepler mission.

Jim Fanson: The Kepler Mission is a space telescope whose objective is to determine if terrestrial planets --- the kind we live on - are common or rare in the galaxy.

The Mercury Transit, I think, reminds us that we live in a family of planets that orbit our stars, and this method of seeing a planet transit, that is, pass between us and the sun and cover part of the sun’s disc, this is exactly the method that the Kepler Mission is going to use to find planets around other stars.

Pitesky: Scheduled for launch in 2008, the Kepler space observatory will stare at one portion of the night sky and monitor the brightness of 100,000 stars, watching for planetary transits. Each transit will cause the star to dim very slightly in brightness. That’s a signal that a planet is passing between Earth and the distant star, just as Mercury will pass between us and a very nearby star - the sun - on November 8.

William Borucki, principal investigator for Kepler, describes the mission as the first step in determining the extent of life in our galaxy.

William Borucki: Kepler is unique in that it's an exploration mission. Basically it has the ability to look at these 100,000 stars. If most of these stars have planets, we would find hundreds of planets in the habitable zone.

The habitable zone is where we think that life could arise. Now we don't believe it can arise on Mercury, for example, which is an extremely hot rock with no atmosphere. We believe it takes an atmosphere, it takes liquid water on the surface. So we’re going to look for planets that are close enough to their star so they’re not frozen solid, but not so close that the oceans have boiled off, like they have on Venus, for example. So the habitable zone, we think, is where life could start out and evolve. And if we find that, life may be ubiquitous in the galaxy. If we don’t find those, and life is very rare, we might be alone.

Pitesky: But Kepler is only the first step in NASA’s long-range quest for new worlds.

Fanson: Part of NASA’s new vision for exploration is to reach out beyond our own solar system to understand what planets may be orbiting other stars, whether there may be other planets like the Earth around other stars. Other missions that NASA has in the planning stages, like SIM PlanetQuest and the Terrestrial Planet Finder, they’re going to be able to detect Earthlike planets around the nearest stars and then follow up by actually taking a family portrait where we can see these planets orbiting, then probe their atmosphere so we can see what kind of chemicals, what kind of chemistry makes up the atmosphere and make very profound conclusions or inferences about the habitability of those planets.

For NASA's PlanetQuest, I'm Dr. Jo Pitesky.

(German anthem)

Announcer: You can find details on how to safely view the Mercury Transit by visiting the PlanetQuest website at http://planetquest.jpl.nasa.gov.