Finding a habitable planet
As we encounter all the successes and setback to environmental sustainability on our planet, there are those keeping up the mission to figure out what makes Earth habitable to begin with and whether life exists elsewhere in the universe.
James Kasting, a geoscience professor at Penn State University and arguably the world’s leader in the study of habitable planets, offered some insights at the California Academy of Sciences in San Francisco on Wednesday.
His new book, How to Find a Habitable Planet, has recently been released and can be considered a primer on the search for other life. Other scientists, namely Peter Ward, author of The Medea Hypothesis (2009), have taken the viewpoint that life is rare in the universe because it is fundamentally harmful in its destabilizing affect on a planet’s climate (an argument hard to refute in today’s age of climate change).
Kasting, a Carl Sagan protege, has a more positive outlook that uses Earth as the prototype in the search for habitable planets. For the purposes of that search, he’s excited by planets that have liquid water on the surface, some semblance of plate tectonics (to cycle carbon), and occupies a “habitable zone” near its star (in relation to the sun, Earth, of course, qualifies while Mars and Venus do not). All those help give a planet an atmosphere, making life possible.
“If you follow climate at all — and it’s hard not to with climate change — you know that surface temperature depends on the greenhouse gas effect,” Kasting said.
Only problem? No planet, except ours, has been found with those qualities.
“Astronomers are finding lots of planets. They’re just not like ours,” he said.
Although lots of research has shown some potential to further the science, Kasting pins his hopes on the Kepler Mission, which is hosted by NASA Ames in Mountain View. Launched in March 2009, the space observatory is monitoring the brightness of 145,000 stars near the Northern Cross. If a planet passes in front of a star, the brightness of the star dims and by this measure the size and the proximity of the planet to the star can be determined.
So far, the results are encouraging. “They found more small planets than big ones in close proximity to stars,” said Kasting. These Earth-sized planets are promising because they’re big enough to hold an atmosphere without being so big that they become a gas planet, like Jupiter. “The most important thing is having solid matter so you can have a surface for life,” Kasting said.
Finding another habitable planet doesn’t mean we’ll embark on a Battlestar Galactic mission to transport ourselves to a newer, less screwed-up planet when the time comes. It’s prudent to still take care of Earth. But we may learn a bit more from other planets about why Earth supports life and how we, as the dominant life form, can keep it healthy.
Disclosure: Alison Hawkes writes a blog on climate change for NASA’s Astrobiology Magazine.