NASA's Kepler mission confirms existence of Earth-sized planets orbiting another star. Photo Credit/NASA Jet Propulsion Laboratory
The last two months of 2011 have produced some remarkable strides in the quest to determine whether life exists elsewhere in universe — at least life as we know it.
Life as we know it, means biological activity in environments where liquid water is stable — not so cold that water freezes and not so hot it boils away.
Two NASA missions — the Kepler space telescope and the Mars Science Laboratory, also known as the Curiosity rover — played a key role in each of these recent advances. This quest still has a long way to go. Fortunately, Kepler’s work is far from over, and MSL’s is just beginning.
“In the cosmic game of hide and seek, finding planets with just the right size and just the right temperature seems only a matter of time,” said Natalie Batalha, Kepler deputy science team lead and professor of astronomy and physics at San Jose State University. “We are on the edge of our seats knowing that Kepler’s most anticipated discoveries are still to come.”
NASA's Kepler space telescope monitors thousands of Milky Way stars for Earth-like planets. Image Credit/NASA image
On Tuesday, Dec. 20, scientists affiliated with the near three-year-old Kepler observatory offered confirmation of the first evidence for Earth-sized planets circling another star. Unfortunately, these worlds, designated Kepler-20e and Kepler- 20f, orbit so close to their star that they are far too hot — 1,400 degrees and 800 degrees Fahrenheit on the surface — for liquid water.
In fact, the surface of Kepler-20e is hot enough to melt glass. Kepler-20f has conditions similar to planet Mercury’s.
The Kepler 20 find is significant because it confirms that Kepler has the sensitivity to detect distant worlds sized like our own. Most of the hundreds of previous alien planet discoveries involved worlds much larger — more like our Jupiter and Neptune.
“The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone,” said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of a report on the latest Kepler find, which was published this week in the journal Nature. “This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them.
The star Kepler 20, is sun-like and resides about 1,000 light years away in the Constellation Lyra.
Earlier this month, on Dec. 5, produced another important Kepler discovery — the first confirmation of a planet, Kepler 22-b, circling another star in the long sought habitable zone, or the orbital realm where water would be stable as a liquid on the surface.
However, Kepler 22-b is a good bit larger than Earth, and the environment is still much a mystery, though the surface is not likely to be rocky like the Earth’s.
The star Kepler 22 is about 600 light years from the Earth.
Kepler 22-b is one of 54 habitable zone alien planet candidates unveiled by Kepler scientists in February of this year. Scientists are still vetting the rest.
“Fortune smiled upon us with the detection of this planet,” said William Borucki, Kepler principal investigator from the NASAAmesResearchCenter, who led the team that discovered Kepler-22b. “The first transit was captured just three days after we declared the spacecraft operationally ready.”
Kepler lifted off on March 6, 2009, initiating a 3.5 year mission to search for Earth-like planets in the habitable zone of other stars. Kepler swung far enough from Earth to monitor more than 100,000 stars in the Milky Way galaxy.
The observatory makes its observations by detecting small dips in the brightness of the stars it monitors. The dimming correlates to the crossing, or transit, of a planet in front of the star..
Nov. 26 brought the launching of the NASA’s Mars Science Laboratory. Now on its way to the Red Planet, MSL is on a course to reach Mars for a landing on Aug. 6.
NASA's Mars Science Laboratory mission begins eight month journey to the Red Planet. Photo Credit/NASA Photo
About the size of a Mini Cooper, MSL will aim for a landing in Gale Crater, a near four- billion-year-old depression more than 900 miles wide with a large mound rising from the interior. Now cold and dry, Mars was once warmer and wetter, experts believe — perhaps a thriving resident of the sun’s habitable zone.
If so, Gale may have been a lake or sea bed. The mound, comprised of layered sediments, likely holds clues about the changing environment of Mars over the ages.
Curiousity is equipped with a sophisticated science lab and was designed to spend two years roaming around its landing site, characterizing the chemical and mineral composition of the soil and rocks. While not able to detect life, MSL can look for the organic chemistry that would be a signature of past or current microbial activity on Mars.
NASA’s latest Martian rover has a nuclear power source as well, enabling it to function in darkness as well as sunlight. Curiosity will build on the work of the smaller solar powered, NASA Spirit and Opportunity rovers that touched down on Mars in early 2004. Opportunity continues to explore well beyond its design life.
Artist's view of Curiosity exploring the Martian surface. Image Credit/NASA Image
Curiosity’s findings may elevate Gale as a target for a future Mars sample return mission. Representatives of NASA, the European and Russian space agencies are discussing the prospects.
Meanwhile, NASA has its eye on Mars as a destination for future human explorers — perhaps in the 2030s.