NASA unveils new model to discover habitable worlds

Scientists at the US National Aeronautics and Space Administration (NASA) say they have come up with a simpler way to find planets that might support life.

The new model helps allocate scarce observing time to the most promising candidates, according to new research published in the Astrophysical Journal.

A star's light illuminating the atmosphere of a planet. /NASA Photo

"Using a model that more realistically simulates atmospheric conditions, we discovered a new process that controls the habitability of exoplanets and will guide us in identifying candidates for further study," said Yuka Fujii of NASA's Goddard Institute for Space Studies (GISS), lead author of the study, in a statement.

NASA has been hot on the trail of Earth-like planets.

Previous studies were forced to rely on one-dimensional and vertical models to simulate atmospheric conditions. The new research uses a model that calculates conditions in all three dimensions, allowing scientists to simulate the circulation of the atmosphere and the special features of that circulation, which one-dimensional models cannot do, according to NASA.

Liquid water is essential to life as we know it. If the temperature of an alien world allows liquid water to be present for sufficient time to allow life to thrive, it is considered potentially habitable. If a planet is too distant from its star, its surface water will freeze; if it is too close, its surface water will evaporate and be lost to space.

This happens when water vapor rises to a layer in the upper atmosphere called the stratosphere and gets broken into its elemental components, hydrogen and oxygen, by ultraviolet light from the star. The extremely light hydrogen atoms can then escape to space.

An illustration compares Earth to a planet beyond the solar system that is a close match, called Kepler-452b. /NASA Photo

Planets in the process of losing their oceans this way are said to have entered a "moist greenhouse" state because of their humid stratospheres.

For exoplanets orbiting close to their parent stars, the team found that the near-infrared radiation (NIR)-driven process could increase moisture in the stratosphere gradually. So, it is possible that an exoplanet closer to its parent star could remain habitable, contrary to old model predictions.

The new approach demonstrated that since these stars emit the bulk of their light at NIR wavelengths, a moist greenhouse state will result even in conditions comparable to or somewhat warmer than Earth's tropics, researchers say.

In the future, the team plans to vary those planetary characteristics, such as gravity, size, atmospheric composition and surface pressure to see how they affect water vapor circulation and habitability.

NEW YORK (AP) — In a rare move, NASA is cutting a mission aboard the International Space Station short after an astronaut had a medical issue.

The space agency said Thursday the U.S.-Japanese-Russian crew of four will return to Earth in the coming days, earlier than planned.

NASA canceled its first spacewalk of the year because of the health issue. The space agency did not identify the astronaut or the medical issue, citing patient privacy. The crew member is now stable.

NASA officials stressed that it was not an onboard emergency, but are "erring on the side of caution for the crew member,” said Dr. James Polk, NASA's chief health and medical officer.

Polk said this was the NASA’s first medical evacuation from the space station although astronauts have been treated aboard for things like toothaches and ear pain.

The crew of four returning home arrived at the orbiting lab via SpaceX in August for a stay of at least six months. The crew included NASA’s Zena Cardman and Mike Fincke along with Japan’s Kimiya Yui and Russia’s Oleg Platonov.

Fincke and Cardman were supposed to carry out the spacewalk to make preparations for a future rollout of solar panels to provide additional power for the space station.

It was Fincke’s fourth visit to the space station and Yui's second time, according to NASA. This was the first spaceflight for Cardman and Platonov.

“I’m proud of the swift effort across the agency thus far to ensure the safety of our astronauts,” NASA administrator Jared Isaacman said.

Three other astronauts are currently living and working aboard the space station including NASA’s Chris Williams and Russia’s Sergei Mikaev and Sergei Kud-Sverchkov, who launched in November aboard a Soyuz rocket for an eight-month stay. They’re due to return home in the summer.

NASA has tapped SpaceX to eventually bring the space station out of orbit by late 2030 or early 2031. Plans called for a safe reentry over ocean.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.

FILE - The International Space Station is seen from the space shuttle Atlantis on July 19, 2011, after it left the orbiting complex. (NASA via AP, File)