The Search for Extraterrestrial Life Continues: TESS and Mars 2020

Apr 23, 2018

The SpaceX Falcon 9
Credit SpaceX

On Wednesday, April 18th, NASA launched a science satellite aboard a SpaceX Falcon 9 rocket for the first time.  After the launch, SpaceX managed to pull off its signature move, landing the first stage of the rocket booster on a barge.

A bonus feature for space geeks – the barge was emblazoned with the words, “Of course I still love you,” a reference to the work of science fiction writer Iain M. Banks.

The satellite aboard that rocket is called TESS, or Transiting Exoplanet Survey Satellite. Once it reaches its elliptical orbit, it will begin its job of looking for earth-like planets around stars nearest to our own solar system.

“TESS has a search radius of something like 300 light years,” said Jennifer Burt, a Torres Exoplanet Fellow at the MIT Kavli Institute. “In astronomical terms, that’s really nearby, but as far as you and I are concerned, that’s not really a distance you see on your GPS very often.”

TESS’s method is to watch for a dip in the amount of light coming from nearby stars.

“The size of the dip tells you how big the planet is, and the timing between those dips tells you how far the planet is from the host star,” Burt said.

That’s important because if the planet is too close to its star, it’ll be too hot for liquid water to exist. Too far from its star, it’ll be too cold for liquid water. There’s a “habitable zone” where the temperature is just right. Once TESS locates planets in that zone, telescopes on the ground can focus in for a closer look.

Despite TESS’s promise, Burt acknowledges that the satellite has her limitations. TESS can only see planets orbiting around stars in the same plane as earth’s orbit. There’s evidence that such orbits are randomly sprinkled throughout the universe.

“Something like 10 percent of systems should have transits that we should be able to see from earth,” she said. “So, for every one planet that TESS sees transiting around a star, there should be another nine stars that also have planets that aren’t oriented quite right for us to detect them with this method.”

MARS 2020

While TESS is off to explore distant exoplanets, there’s an ongoing search for extraterrestrial life much closer to home.

Scientists are still searching the Mars for evidence of life – probably past life, but possibly present. A new rover will head to Mars in 2020, and right now, the science community is hashing out where it will land and where it will focus most of its attention.

But, we’ve already sent rovers to Mars, which have sent back excellent photos. If Mars had life on it, wouldn’t we know it by now?

“If Mars were teeming with life, we would have found it. But, clearly, Mars is not teeming with life,” said Jack Mustard is Professor of Earth, Environmental, and Planetary Sciences at Brown University.

Mustard is deeply involved in the process of selecting a landing site and planning the science the next rover will do once it gets there.

“We’ve barely scratched the surface,” Mustard said. “And if I were a microbe living on Mars, I would not be on the surface, I’m telling you. I would be underground.”

Mustard says that signs of life on Mars would most likely be of past life, not present.

“The ground is probably frozen down to a kilometer depth,” Mustard said. “It would be hard to live…near the surface.”

NASA started the process of selecting a landing site for the rover in 2011 and has been taking public input. A working group of scientists has narrowed down the sites from more than 30 proposals to just three finalists.

They will hold the final meeting to select the landing site at the end of September.

“[We’ll] really have a detailed science discussion,” he said.

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