During a panel discussion on Tuesday, April 7 NASA chief scientist Ellen Stofan had some exciting news:
“I think we’re going to have strong indications of life beyond Earth within a decade, and I think we’re going to have definitive evidence within 20 to 30 years,” Stofan said.
However, Stofan and the team of panelists were less sure about exactly where humankind will discover the first signs of alien life.
“I think we’re one generation away in our solar system, whether it’s on an icy moon or on Mars, and one generation [away] on a planet around a nearby star,” said another panelist member and associate administrator for NASA’s Science Mission Directorate John Grunsfeld.
Last month, Business Insider spoke with NASA astrobiologist Chris McKay about where he thought humankind would first find signs of alien life in our solar system. Surprisingly, the most likely place is not nearby or on any surface.
Where to begin
We need to start looking underground, according to McKay.
“Things are better below the surface,” says McKay, who is a senior scientist with NASA’s Planetary Systems Branch. She investigates where else life could exist in our solar system.
Unfortunately, designing and dispatching a lander that can dig deep beneath a planet’s surface is incredibly difficult and expensive. The only places scientists have drilled, collected, and examined samples beneath the surface is on the moon and Mars.
One place where we wouldn’t need to dig and drill is on Saturn’s tiny moon, Enceladus. It harbours a massive ocean underneath a thick layer of ice on its surface. Two different teams of scientists found compelling evidence there that indicates active volcanoes line the tiny moon’s seafloor.
McKay is excited about the prospect of Enceladus for another reason though. “Enceladus is most likely to give us an answer soonest,” he said. “The reason is Enceladus has a plume coming into space.”
In 2005, the Cassini spacecraft flew by Enceladus and spotted plumes of water vapour and other materials gushing out of its surface. If there’s life in the solar system, the first place we’re likely to find it is inside of those plumes, McKay said.
What to look for
Sadly, Cassini is not equipped with the right instruments to detect signs of life in these plumes. And right now, NASA has no plans to dispatch another probe to Saturn or its moons anytime soon. That’s not stopping McKay and others from discussing what they’d look for there if they had the chance.
“I’d suggest that the best molecules to measure are amino acids, the building blocks of proteins,” McKay said during a live webcast hosted by The Kavli Foundation in January. “Life on Earth has made specific choices in amino acids. It uses a set of just 20 amino acids to build proteins, and those amino acids are all left-handed.”
Left-handed amino acids are chemically identical (meaning they have all the same atoms in the same amounts) to right-handed animo acids. The difference is that they are structured in a way so they’re mirror images of one another, just like how your right and left hands are the same shape but don’t line up when you put one on top of the other.
One of the outstanding mysteries in astrobiology is why RNA and DNA is only constructed from proteins built by left-handed amino acids. Regardless of why or how, this fact will come in handy during potential future studies of Enceladus.
“If Chris were to find amino acids in the plumes of Enceladus, the challenge becomes determining whether they are the products of a biological process,” Steven Benner, president of the Foundation for Applied Molecular Evolution in Florida, said during the webcast. “If he were to find that they’re all the same hand, that would be convincing, because that’s what makes the protein evolvable.”
The real question: how different will aliens be from us?
For McKay, the excitement of the hunt is not just about discovering whether aliens exist. It’s discovering unique alien life that is completely different from life on Earth, which might be quite a bit harder since the building blocks of life are so complex.
“In my mind that’s the real question. Not, ‘Is there life on these other worlds?’ but ‘iI there a second genesis of life on these other worlds?'” McKay told Business Insider. “That’s a subtlety that’s not obvious until you think about it.”
A second-genesis of alien life could, in theory, have a completely different biomolecular structure from life on Earth. Right now, scientists debate whether or not life on Earth originated on another celestial object, like Mars, that then hitched a ride to Earth inside of a meteorite.
That is not a stretch to imagine, researchers say, since Mars was covered with liquid water around the same time that life is believed to have begun on Earth. If we do find evidence of life on Mars and it has the same DNA as us, then it’s probably our cousins, McKay told Business Insider.
If we want to find truly unique alien life, then we’ll have to travel farther than next door.
“As we go from Mars to Europa to Enceladus to Titan, as the worlds get farther away from Earth the conditions get less and less like Earth,” McKay said. “We’re more likely to find life that’s not related to us the farther out we go.”
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