Humans have asked for thousands of years whether there is life elsewhere in the Universe, but in the last few decades, great advances have been made in our quest for signatures that indicate towards life outside of our own Solar System.
NASA programs, including the Kepler Space Telescope, have helped scientists tremendously in documenting thousands of exoplanets, which are basically planets that orbit around other stars than our Sun.
Other more new NASA missions, such as the Transiting Exoplanet Survey Satellite (TESS), are expected to largely enhance the current number of found exoplanets. The experts are awaiting the powerful scientific instruments to find Earth-size rocky planets rotating around their stars’ habitable regions, at distances where water could exist in liquid form on their surfaces.
Exoplanets Similar to Earth
This is expected to be accomplished by missions like the future James Webb Space Telescope, which will add to and extend the findings of the acclaimed Hubble Space Telescope by monitoring space at infrared wavelengths.
The new instrument is set to launch in 2021 and will enable scientists to figure out whether rocky exoplanets have oxygen in their atmospheres, which could be a sign of life. However, not all exoplanets will be similar to Earth, and that’s why researchers are trying to narrow down the field of those for which oxygen is most suggestive of life.
To narrow down the ground, scientists led by Arizona State University have come up with a method called ‘detectability index,’ which may help give priority to exoplanets that need more study. The complete explanation of what this new index is and how it works has been published in the Astrophysical Journal of the American Astronomical Society.
“The goal of the index is to provide scientists with a tool to select the very best targets for observation and to maximize the chances of detecting life,” explains lead author Donald Glaser of ASU’s School of Molecular Sciences.
Using the Detectability Index to Search For Life
The oxygen detectability index for a planet similar to Earth is high, which means that oxygen in our planet’s atmosphere is certainly due to life and nothing else. The team of scientists has found that the detectability index plunges for exoplanets not that different from Earth, which is rather surprising.
Even though Earth’s surface is mostly covered in water, the planet’s oceans make up a small percentage (0.025%) of Earth’s mass. In comparison, moons in the outer Solar System usually have about 50 percent water ice.
“The detectability index tells us it’s not enough to observe oxygen in an exoplanet’s atmosphere. We must also observe oceans and land,” says co-author Steven Desch of ASU’s School of Earth and Space Exploration. “That changes how we approach the search for life on exoplanets. It helps us interpret observations we’ve made of exoplanets. It helps us pick the best target exoplanets to look for life on. And it helps us design the next generation of space telescopes so that we get all the information we need to make a positive identification of life.”
The creation of the team of researchers was funded by NASA’s Nexus for Exoplanetary System Science (NExSS) program, which funds interdisciplinary studies to create strategies for looking for life on exoplanets.