A new viral video details the efforts that NASA is making to find out whether we are alone in the universe.
In the video, which at the time of writing has been viewed almost 1.8 million times, NASA astrobiologist at the Goddard Space Flight Center Heather Graham explained what actions the space agency is taking to hunt for the signs of alien life.
The video is hosted by Australian YouTuber AstroKobi, also known as Kobi Brown, who explains in the video that the NASA astrobiology program is currently working to address three fundamental questions: How does life begin and evolve? Does life exist elsewhere in the universe? And how do we best search for life in the universe?
Graham says to even begin considering these questions, scientists must first understand what life actually is, with Brown explaining that life isn't just creatures like humans, but can include a range of radically different organisms.
Related: Life on Mars: Exploration and evidence
"Everywhere we go on this planet, we see life, down at the very bottom of the ocean in the deepest sediments, encased in ice, and at the top of dry mountaintops," Graham said in the video. "We don't actually know yet how life on this planet began, and it's really a hard and tricky problem to get at because the Earth has looked wildly different over its history."
This means, she added, that "rolling back clock" on Earth means considering environments that are now very foreign to us, with the fossil record providing examples of organisms that were, at one time, best suited to these different environments. That means when NASA is considering how life began, it has to think about how any life could begin.
"When we start to look at life this way and realize that life is this grand conversation happening with its environment, it makes it easier for us to imagine that on other planets, they also have rich histories, and they also may have been many planets over the course of their lifetime," Graham said. " And even more significant, this means that they may have also been able to accommodate many different types of life."
As Graham pointed out, however, the fact that water is essential for all life as we understand it, as is energy from a star or another source and an environment that promotes the chemistry unique to life, narrows the search down somewhat.
Small lifeforms would be a big deal
The main type of life that NASA concentrates on in the solar system is microscopic life forms or microorganisms. Though a world away from little green men crashing spacecraft into backyards in rural America as is often envisioned, Graham explains that the discovery of microbes on another world would be of tremendous importance. And given the history of our own world, hunting for microbes as a form of alien life makes complete sense.
"We have to remember that the majority of our history has been microbial. Microbes were in charge of our planet for some three billion years before bigger organisms even showed up. If you think about the grand history of the Earth, it was a micro world for 70% of its existence," Brown explains. "If we find a microbe, it means we found a planetary chemistry that discovered how to build life. Yeah, maybe we wouldn't be able to talk to it, but at least we would know that we aren't alone and life isn't a one-off occurrence."
Currently, one of the most intense searches for microbial life is underway on Mars, where the robotic rovers Curiosity and Perseverance are exploring regions that billions of years ago overflowed with abundant water in stark contrast to the barren and arid planet seen today. It is hoped that the rocks of these fossilized waterways of Mars could contain within them traces of ancient microbial life.
"A great example of a mission that's using chemical biosignatures is the Curiosity Rover on Mars," Graham said. "On that rover is an instrument called SAM [Sample Analysis at Mars], and it's basically an entire chemistry lab stuffed down into something about the size of a big microwave oven. Right now, on the surface of Mars, it's taking rock and pulling out organic molecules that we think might be possible chemical biosignatures."
The astrobiologist also pointed out that scientists from NASA and the European Space Agency (ESA) are hard at work devising a Mars sample return mission that will pick up tubes dropped on the Martian surface by Perseverance and return them to Earth for analysis.
And Mars isn't the only place where NASA is collecting samples.
"We are all madly working to get ready for the return of Bennu, the asteroid sample that's coming to us from OSIRIS-REx in September of this year," Graham said.
Understanding asteroid samples is important because these space rocks are believed to have formed from the material that also birthed the planets. Unlike samples of asteroids that break away and land on Earth as meteorites, the samples returned by missions like OSIRIS-REx will be protected from the effects of entering Earth's atmosphere at high speeds, thus offering a more "pristine" look at the matter that formed our planet. This could also reveal potential organic molecules essential to life, implicating that these molecules could have been delivered to our planet in its infancy by space-rock impacts.
Some moons orbiting other planets of the solar system are also of particular interest to NASA in its ongoing search for life beyond Earth. Ocean worlds like Enceladus, the sixth-largest moon of Saturn, and Europa, a moon of Jupiter, are especially enticing targets.
"A mission coming up that I'm really excited about is the Europa Clipper launching next year. When we get better imagery [of Europa] we'll be able to better understand if it's a geologically active world," Graham said. "Previous missions suggest that at the bottom of Europa's oceans, there could be hydrothermal vents or openings in the sea floor."
She added that these openings heat water and could fuel life beneath the icy shell of Europa, an ecosystem that sunlight struggles to reach. "On Earth, we see those same hydrothermal vent systems on our own sea floor as an oasis for life fueled by chemical energy," the astrobiologist continued.
Graham also highlighted the potential of the James Webb Space Telescope (JWST) to hunt for traces of life beyond the solar system. The grand telescope can detect biosignatures around extrasolar planets or "exoplanets" that indicate something in the atmosphere of these worlds orbiting other stars is using energy in that environment.
"We may not know yet how life began on this planet, but we've learned how varied life is, and given time, how little it needs to rise," Brown concludes. "We also got a glimpse into some of the tools for how to detect it, and we found a possibility that life could have arisen beyond Earth and is somewhere hidden in the universe yet to be discovered. But my key takeaway is that today, we live in a world that is extraordinary and full of possibilities."
The Curiosity image can be seen in its full glory here, with users able to switch between a plain and an annotated view of Mars.
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