Nasa's New Telescope Won't Be Able to Tell How Likely Alien Life Is on New Planets—This Is Why

On Monday evening, NASA is due to launch its new telescope, the Transiting Exoplanet Survey Satellite, or TESS. The instrument's main job is to identify exoplanets, planets orbiting stars other than our own sun.

Scientists estimate the project will identify thousands of planets we've never seen before. But if you have your heart set on finding evidence of extraterrestrial life, TESS is just the first step—it won't be able to gather quite enough information about these new planets to get a good sense of how habitable they might be.

"This is all supposed to be orchestrated in a way that TESS will find the objects, and then other current and future telescopes will be able to do the characterization of their atmospheres," TESS scientific leader George Ricker, an astronomer at MIT, told Newsweek.

Read more: NASA Is Launching Its Next Planet-Hunting Telescope, Here's What to Know

The new telescope works by watching stars and looking for the tiny repeated dips in their brightness caused by a planet passing between the telescope and the star. "You don't really have an image," Ricker said.

From just that brightness data, TESS scientists will be able to differentiate between real planets and false signals like those caused by debris or instrument flukes. They will also be able to parse out some important details about each new planet, like its size and how it orbits its star.

Ground-based telescopes already in operation will add the planet's mass, which in turn lets scientists calculate how dense it is. That can give some sense of whether a planet has a large metallic core like Mercury or is full of lighter ingredients, but not much detail.

An artist's conception of what TESS will look like in action. NASA's Goddard Space Flight Center

Scientists will then identify which of TESS's planets they'd most like to learn more about for further study. "TESS itself will not be able to find life beyond Earth, but TESS will help us figure out where to point our larger telescopes in that search," Paul Hertz, head of the astrophysics division at NASA, said during a press conference on March 28.

Of particular interest to TESS scientists is the James Webb Space Telescope, which NASA is planning to launch in 2020. That instrument will be able to identify some of the molecules found in an exoplanet's atmosphere, which is a crucial step to understanding what it would be like on the surface.

"Are they lava worlds, are they water worlds, are they rocky worlds with thin atmospheres like the Earth?" Hertz said during the press conference. "That's what we're gonna learn, and we don't know the answer to that question yet."