It's understandable that – as planets go – Geoff Marcy has become a bit demanding by now. The astronomer at the University of California, Berkeley, is the most successful planet hunter of all time, discovering more than 70 exosolar planets, most of them gas giants like our own Jupiter.

"It's true that finding a Jupiter is a little bit ho-hum," he told Deutsche Welle. "Saturns don't get me up in the morning, nor do Neptunes. But with this Kepler telescope, we're getting so close to finding new Earths that the hairs on the back of my neck are standing up."

According to Marcy, the introduction of the space-based Kepler telescope, named after the renowned 17th century German astronomer-mathematician, Johannes Kepler, has been a game-changer in the race to discover extraterrestrial life. It launched in March last year, equipped with the largest camera ever sent into space, and is expected to continue sending information back to Earth until at least November 2012. Kepler has so far identified more than 700 exosolar planets, or planets outside our solar system, in what is NASA's first mission in search of Earth-like planets.

The hard part is carrying out painstaking analysis of each and every planet candidate using Earth-based tools to search for one that's similar to our own and which would likely harbor other life forms.

"The search for Earth-like planets is the highest priority in my life and the lives of several hundred astronomers who are working with me," Marcy said.

Looking for another Earth

The analysis of exoplanets from Earth is anything but easy. Scientists basically rely on two indirect tools to calculate the planet's mass and radius. To determine mass, they measure what is called the "wobble." When a planet orbits, its gravity tugs on its star. Mass is ascertained by measuring the dimming effect. When a planet transits between its sun and the observing telescope, the light from the star becomes a little bit fainter.

Earth-like planets, said Marcy, are small, and have such little mass that they barely make a gravitational tug on the host star. "And because it's such a small speck of dust, an Earth-like planet doesn't block very much starlight when it crosses in front of the star," he said.

The next important question to be answered for a candidate to have a chance of supporting life is: Does the exosolar planet have an atmosphere? Kepler's next mission will be to check for atmospheres on those of the 700 plus candidates that have a similar size and temperature to Earth.

Tools of tomorrow

But according to Kepler's chief scientist, Bill Borucki, analyzing the precise make-up of a given atmosphere requires new tools that haven't been built yet.

"You would need to launch a telescope that focuses on the light of the star and you would use spectrometers to measure the atmosphere and see whether there was oxygen in it," he said, in an attempt to explain what these future tools would entail.

A spectrometer measures light waves. And since every molecule reflects or absorbs light in a characteristic manner, scientists would know which elements and compounds can be found in that distant atmosphere. But such analysis would cost billions of dollars. And with the current level of propulsion technology, people will never be able to reach solar systems found light years away from Earth. So why do it?

"Once upon a time, if you wanted to go from one place to another and there was a river in the way, you had to swim," says Borucki. "Then we built rafts and dug out canoes. But we still couldn't get to the moon. Well, we figured out how to get to the moon, and now we're going to Mars."

In other words, if tomorrow's generation is seriously thinking about how to reach the stars, then they'll find some way to make it happen.

Author: Madeleine Amberger (dc)
Editor: Mark Mattox