The Search for Life Across the Universe

Smithsonian astrophysicist Jeremy Drake explains how the question changed from “if” life will be found elsewhere to “when” and “where”

The planet Kepler-22b, shown in this artwork, is the right size and distance from its star to support liquid water, and perhaps life. NASA/Ames/JPL-Caltech

When Jeremy Drake was beginning his career in the late 1980s, the question of whether or not we are alone in the universe still seemed beyond the realm of science.

“It was like how we can’t prove or deny the existence of God,” Drake says. “There was no data.”

A lot has changed since Drake, now 49 and a senior astrophysicist at the Harvard-Smithsonian Center for Astrophysics, began studying stars as a doctoral student at Oxford.

In the mid-1990s, more advanced telescopes and spectrometers revealed the first planets orbiting distant stars—a discovery that, for the first time, opened up the tantalizing possibility of life elsewhere in the galaxy. Over the years, the number of known planets has exploded to more than 1,700. Just last month, NASA announced that its Kepler space telescope, launched in 2009, had enabled the identification of 715 new planets orbiting 305 stars, including four that are the right size and distance from their stars to support liquid water, and thus life as we know it.

While it’s unlikely we’ll be able to examine these planets closely any time soon, scientists are beginning to do the fundamental research that could one day help determine which newly-discovered planets have the greatest chance of hosting extraterrestrial life. And much of that work is now happening at the Smithsonian.

In 2012, Drake, whose lab sits on a hill in a quiet corner of Harvard’s campus, organized a conference called “Life in the Cosmos” in Washington, D.C., bringing together Smithsonian scientists from such disparate institutions as the Natural History Museum, the Air and Space Museum and the Smithsonian Tropical Research Institute in Panama. While at first glance an astrophysicist might seem to have little in common with paleontologists or rainforest ecologists, Drake hopes the cross-disciplinary collaborations that arise from this project will help us better understand the origin of life on Earth—and how it might develop elsewhere in the galaxy.

“This is the broadest scientific problem,” he says. “And in my mind, it’s perhaps the most important question.”

What are the chances that there’s life out there?

The situation changes so fast. Before 1995, we had no idea—we only had one known solar system. [In 1961] the Drake Equation—different Drake, of course—said, basically, that determining the probability of the number of planets in the galaxy is pure guesswork. Around 1980, we first began to see these things called “dusty disks” around solar-like stars, and bigger and better missions saw these in greater numbers. That brings us to the era of planet detection, starting in the mid 90s. Of course, these first planets were very close to their parent star, gas giants with no chance of harboring life at all. And that’s because those were the easiest ones to detect. But we now realize that there’s a very high probability of more Earth-like planets around stars. There may be other ways to develop life that doesn’t necessarily need planets, but certainly the easiest way is to have some sort of stable environment, like a planetary system that has energy input from a nearby star. So, planets are a good bet.

How did you come to organize “Life in the Cosmos”?

It was probably 2010, and I was studying the outer atmospheres of stars, which is referred to in the Sun as the solar corona. There was already substantial data on planet existence, and I started thinking about what the radiation environments of planets would be. I thought that could be linked to what other people were doing, people like Bob Craddock at the Air and Space Museum, who has been studying a very important problem in planetary physics: How did Mars lose its atmosphere? If you want to have life on a planet, that’s not something you want to happen.

It’s been a couple of years since you held the conference in Washington. Have any interesting studies or collaborations come out of it?

Yeah, there are some studies, some potential collaborations that are still in infancy. The main problem in science is always money. We’re applying to fund a five-year study on how the building blocks necessary for planet habitability are assembled. We have another proposal to look at the atmospheric evolution of planets. We had a seed project, with the people down in Panama [at the Smithsonian Tropical Research Institute], looking at how phosphorus availability is going to affect ecosystems. Phosphorus is needed for life, but it’s actually very short lived in an active planet because it gets leeched out of the soil by normal weather. It’s replenished in the Earth by geological activity—so how important is geological activity to the development of life? We don’t really know that. Something like plate tectonics on the Earth, is that a requirement for life elsewhere?

Is the idea that, eventually, once we have better technology to look at these newly discovered planets, this research could help us pick which ones warrant further study, or which may have the greatest probability of supporting life?

That’s quite right. Probably plate tectonics is too difficult to predict in terms of modeling a planet at this point, but maybe you could understand grossly what planets should have that characteristic. Or you could say, “Okay, if we have limited resources, let’s go with the planets we think have the right atmosphere.” You’d try to find the ones that are interesting. That number may be vague, but it’s certainly not going to be the majority.

How does your own research contribute to answering these questions?

I’m working on protoplanetary disks, and also where stars are formed. Planets probably form relatively quickly at the same time that the star is finishing its formation. It’s a very, very complicated but very interesting astrophysics problem. What we do is use this high x-ray contrast in young stars to basically find the young, forming solar systems, and then look for protoplanetary disks. These studies give us an idea of how many planets there may be in the galaxy.

If we do find it, what might life on other planets look like?

I suspect that what’s going to happen is we’re going to find a planet with a detectable oxygen signature, and probably that will betray bioactivity, probably primal ooze or bacteria. My suspicion is if we detect anything—and provided the planet’s not too dissimilar to Earth—it’s going to look like something we’re vaguely familiar with. Just numerically, life didn’t really get going here in a much more sophisticated way until hundreds of millions of years ago rather than billions, and the most common thing here is bacteria. But then again, I’m not a biologist, so maybe something that looks the same to me would look totally different to a biologist.

What about life based on a totally different chemistry—silicon, for example?

I don’t think so. That’s something that was briefly raised a while back, but my suspicion is that life arose on Earth the way it did because of fundamentals in biochemistry, and that those fundamental processes are universal, rather than peculiar to us. We know we’ve had this strain of life on Earth for billions of years, and chemistry has had a chance to do other things if they really worked.

There has been a lot of talk about extremophiles—life here on Earth that exists in geothermic vents and other harsh environments—as a possible model for life on other planets. Do you think that’s a possibility? 

Extremophiles are often used as an argument for saying how different life could be than what we currently are most familiar with. I, personally, have the opposite argument. I think that what happens is once you give a foothold to life, then it has the ability to adapt to more bizarre environments. I don’t think that necessarily tells you that life can originate in bizarre environments. My suspicion is you need to have fairly Goldilocks-like conditions for life to get going, but once it does you have the possibility of creating things that are much more exotic.

Of course this whole quest is still in the very early stages, but if we do discover life elsewhere in the galaxy, what are the chances we’ll be able to visit it?

In order for us to visit another civilization, or for them to visit us, there has to be a part of physics that’s not yet understood. You can’t do it, traveling at the speed of light. In order for civilizations to travel galactic-type distances, there has to be an unknown physics that allows that to happen. If that does happen, it has huge implications for our lack of understanding of basic physics. There’s one of the arguments against the UFO phenomenon, at the moment: Physically, it’s just not possible.

Even if we can’t reach newly discovered extraterrestrial life, what would be the impact of the discovery here on Earth?

I think it would have an enormous impact—psychologically, theologically, socially. But I think that would be the biggest single scientific discovery in history, one of the most important things that humans have done. Right now we have a country-wide approach to life—an “us against them,” nationality type of thing. I think if life were detected on other planets, and certainly if communication or signs of civilizations were found, I would hope the perspective would entirely change. We’d become more outward-looking. Would humans feel less self-important? Maybe they would. That’s probably a good thing. 

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