Above: Venus, photographed by the Galileo spacecraft in 1990. [More]

Picture this: A spaceship swoops in from the void, plunging toward a cloudy planet about the size of Earth. A laser beam lances out from the ship; it probes the planet's clouds, striving to reach the hidden surface below. Meanwhile, back on the craft's home world, scientists perch on the edge of their seats waiting to see what happens.

Sounds like science fiction? This is real, and it's happening today.

The spacecraft is MESSENGER, and the planet is Venus. On June 5, 2007, MESSENGER will fly past Venus just 338 km above the planet's surface--and it will shoot a laser into the clouds.

MESSENGER is on a mission to Mercury, not Venus. But the spacecraft must pass by Venus for a gravity assist en route. In passing, researchers hope to learn a few things about Earth's "evil twin," an Earth-sized world with sulfuric acid clouds, a choking carbon dioxide atmosphere, and a surface hot enough to melt lead.

Of particular interest is the laser experiment, which aims to measure the location of Venus' cloud decks. "It could either fizzle or be a major result," says Ralph McNutt, MESSENGER's project scientist at the Johns Hopkins University Applied Physics Lab. "We've never sent a laser to Venus before. This could give us some unique information about the planet's clouds."

The name of the laser is MLA--short for Mercury Laser Altimeter. It was designed to map the rocky topography of Mercury, but MLA turns out to have some nice properties for the study of Venus. Solomon explains: "Venus' atmosphere and clouds are nearly transparent at several infra-red wavelengths." The wavelength of the laser (1064 nm) is close to one of these spectral "windows," so it may be able to penetrate deep into the atmosphere. "It's a long shot, but we may even see returns from the surface of Venus," he speculates.

Right: The Mercury Laser Altimeter, MLA. The central laser is surrounded by four receiver telescopes. [More]

 

See you in the ether !