Peter Smith

The more you learn about life on the Earth and the incredible things it’s done to adapt to strange environments—for instance, even here in Tucson, look at the Palo Verde trees. If you take a seed off a Palo Verde tree and put it in some nutrients and add water, it will not grow. Why not? Because its seed coating is so tough that water can’t penetrate. The only way a Palo Verde tree can sprout is if the seed, which has landed on the ground, runs along a stream and wears off the outer part of the seed coating. Then it will sprout. So it only sprouts when it’s wet. How does a tree know how to do that? That is really clever. And that’s just one out of a billion example of how life adapts.

Life came almost instantly on the Earth after it cooled. Mars would have cooled first, and water would’ve been stable on the surface. There’s probably lots of water on Mars. Certainly we see remnants of it today. Why wouldn’t have life formed immediately there? And if it did, why can’t it adapt as ferociously as life has on the Earth to every little niche and cranny, including, as the water dried up, underground? It would’ve gone right underground with the water, wouldn’t it?

I don’t know if the ice in the northern plains of Mars is where life took hold or not, but it’s a good chance. That’s where water comes up to the surface. There’s ice all under the surface, probably all around Mars. This is the one place you can get to it. So we’re hopeful. What are the chances? I try to keep myself from getting too excited. Basically we’re throwing a dart at a map, and what are the chances that that’s the place? I am feeling lucky though.

Dante Lauretta

There’s no evidence for it, so scientifically we have to say that the jury is out. Based on my studies of the origin of life and the chemistry involved with basic processes I’d say it is very likely that biology is going on somewhere else in this universe. We haven’t figured out exactly how the origin of life started, but we’ve got a pretty good framework for how it could get going. Nothing seems like a show-stopper right now. There are some critical steps we need to work out, like how you make up a polyimide molecule, but all the basic building blocks are there and they’re very common. So I would say yes, there’s a high probability. There’s just no evidence for it, or against it.

Renu Malhotra

I’ve wavered with this, being pessimistic and optimistic. At this point I’m pessimistic, and the reason is that there are so many things that have to go just right, for an Earth-like planet as we find it today. A lot of things have to come together just right, just so: Quite narrow ranges of physical parameters and initial conditions for Earth to be comfortable for life, particularly advanced life.

But then, you know, it’s a pretty ill-defined question. How close do conditions have to be for us to say that some alien planet is an Earth-like planet? Conditions may be equally exciting and interesting on other planets, other worlds, but totally different than on ours. 

Alexander Pavlov

Astrobiology is a new direction in science, which is really on the border of biology, astronomy, planetary science, and atmospheric science. People are interested in the origin of life and specifically how life evolved together with the environment, and whether life can be present on other terrestrial planets like Mars or elsewhere in the universe.

You really have to go to the boundaries of these disciplines to answer those questions. That’s why NASA has this new initiative to essentially sponsor that new direction which we call astrobiology. My interest in the astrobiology is from the climate standpoint. I want to know what kind of environment and what kind of climate was there at the moment of the origin of life, at the early evolution of life in particular.

The main interest is to study Mars, because Mars—I won’t say it’s the only place we expect to find extraterrestrial life in the solar system, but it’s the most reachable place. There are other potential places like Titan and Europa, but they’re much further away, although they’re extremely interesting as well.

But Mars is relatively accessible and there’s a whole kind of express of missions that’s being developed. It is important to know where exactly you’d expect some kind of life, if life was there. There are all sorts of questions we can get from the atmosphere. The discovery of methane on Mars is a very strong indication of life. But is that true? Is it confirmed that this is a direct sign of biology, since methane is a biogenic gas? So there are a lot of things that atmospheric science can give you. That’s why I see myself entering into this field.

The beauty of astrobiology is that you can have an idea and you’re working with scientists in different disciplines, biologists in particular. Biologists don’t know anything about planets or the Martian atmosphere, really. But if you know how the climate works and what to expect on the Martian surface, you can give a biologist a clue on how to set up a particular experiment in order to test what particular bugs are going to live there or not.

I think there’s a very strong indication [that there could be life on Mars]. There are so many suggestions that, well, the UV radiation is a problem, lack of water is a problem, ionizing radiation, superoxidants is a problem. It is a harsh place, there’s no question of that. It’s cold there. But the more we start learning about extremes of life, we’ll be smarter where to look. Don’t go to directly the surface, go a little bit underneath. You have ice there. The water is maybe not stable at the Mars surface because of the very low pressures. But if the ice is underneath, all of a sudden we have a layer that has water in it, liquid films. Yes, it’s not as stable as an ocean, but how much do you really need for the microorganisms to survive? Not much.

When you start doing all this, then the objections that people have about life on Mars kind of fall. You find out that, yes, there are bugs here which live in the Siberian permafrost, with conditions very similar to what’s there. There are microorganisms that can take extremely high dosages of radiation. The fact that Mars doesn’t have a magnetic field, and a very thin atmosphere bombarded by cosmic rays, is really nothing strange either. So really there’s no reason why not. I think we’ll be witnesses to this kind of discovery being made.

Guy Consolmagno

Oddly enough, I think it will be a three-day wonder and then people will be worried about Britney Spears again. The fact is I don’t think it will be a radical shift in anybody’s thinking, because I think everybody expects it to happen sooner or later anyway. By the time it does happen, the reaction will be, “Well, it’s about time,” or “Didn’t they already know that?” Even if it was intelligent life. I think, also, if we do find intelligent life we’ll find out that their way of communicating, their kind of language, is so utterly alien from ours that we won’t be able to communicate. But, who knows? I still read that science fiction, and anything’s possible.

John Lewis

You look at our little eight or nine, or eight-and-a-half, planets and think that that’s a fair representation of all that planets can be—uh-uh. It’s just a small taste. There are many other possibilities. The purpose of my book Worlds Without Endwas to spell out some of those other possibilities, and to open people’s eyes as to why a few government dollars properly spent on discovering planets of other stars might tell us an enormous amount about our own Solar System, our own Earth, its relationship to the other planets, and the big questions: Are we alone in the universe? Are habitable planets possible?

There’s sort of a popular misconception that the reason the Earth is inhabited is become we have oceans and a wonderful oxygen atmosphere, but in fact the reason the oceans aren’t frozen is because we have life on Earth regulating the composition and thermal properties of the atmosphere, and the reason we have oxygen in the atmosphere is because plants grow. Earth has adapted to life.