Placeholder Image

Subtitles section Play video

  • Well, you know, sometimes

  • the most important things come in the smallest packages.

  • I am going to try to convince you, in the 15 minutes I have,

  • that microbes have a lot to say about questions such as,

  • "Are we alone?"

  • and they can tell us more about not only life in our solar system

  • but also maybe beyond,

  • and this is why I am tracking them down in the most impossible places on Earth,

  • in extreme environments where conditions

  • are really pushing them to the brink of survival.

  • Actually, sometimes me too, when I'm trying to follow them too close.

  • But here's the thing:

  • We are the only advanced civilization in the solar system,

  • but that doesn't mean that there is no microbial life nearby.

  • In fact, the planets and moons you see here

  • could host life -- all of them -- and we know that,

  • and it's a strong possibility.

  • And if we were going to find life on those moons and planets,

  • then we would answer questions such as,

  • are we alone in the solar system?

  • Where are we coming from?

  • Do we have family in the neighborhood?

  • Is there life beyond our solar system?

  • And we can ask all those questions because there has been a revolution

  • in our understanding of what a habitable planet is,

  • and today, a habitable planet is a planet

  • that has a zone where water can stay stable,

  • but to me this is a horizontal definition of habitability,

  • because it involves a distance to a star,

  • but there is another dimension to habitability,

  • and this is a vertical dimension.

  • Think of it as

  • conditions in the subsurface of a planet where you are very far away from a sun,

  • but you still have water, energy, nutrients,

  • which for some of them means food,

  • and a protection.

  • And when you look at the Earth,

  • very far away from any sunlight, deep in the ocean,

  • you have life thriving

  • and it uses only chemistry for life processes.

  • So when you think of it at that point, all walls collapse.

  • You have no limitations, basically.

  • And if you have been looking at the headlines lately,

  • then you will see that we have discovered a subsurface ocean

  • on Europa, on Ganymede, on Enceladus, on Titan,

  • and now we are finding a geyser and hot springs on Enceladus,

  • Our solar system is turning into a giant spa.

  • For anybody who has gone to a spa knows how much microbes like that, right?

  • (Laughter)

  • So at that point, think also about Mars.

  • There is no life possible at the surface of Mars today,

  • but it might still be hiding underground.

  • So, we have been making progress in our understanding of habitability,

  • but we also have been making progress in our understanding

  • of what the signatures of life are on Earth.

  • And you can have what we call organic molecules,

  • and these are the bricks of life,

  • and you can have fossils,

  • and you can minerals, biominerals,

  • which is due to the reaction between bacteria and rocks,

  • and of course you can have gases in the atmosphere.

  • And when you look at those tiny green algae

  • on the right of the slide here,

  • they are the direct descendants of those who have been pumping oxygen

  • a billion years ago in the atmosphere of the Earth.

  • When they did that, they poisoned 90 percent of the life

  • at the surface of the Earth,

  • but they are the reason why you are breathing this air today.

  • But as much as our understanding grows of all of these things,

  • there is one question we still cannot answer,

  • and this is, where are we coming from?

  • And you know, it's getting worse,

  • because we won't be able to find the physical evidence

  • of where we are coming from on this planet,

  • and the reason being is that anything that is older than four billion years is gone.

  • All record is gone,

  • erased by plate tectonics and erosion.

  • This is what I call the Earth's biological horizon.

  • Beyond this horizon we don't know where we are coming from.

  • So is everything lost? Well, maybe not.

  • And we might be able to find evidence of our own origin

  • in the most unlikely place, and this place in Mars.

  • How is this possible?

  • Well clearly at the beginning of the solar system,

  • Mars and the Earth were bombarded by giant asteroids and comets,

  • and there were ejecta from these impacts all over the place.

  • Earth and Mars kept throwing rocks at each other for a very long time.

  • Pieces of rocks landed on the Earth.

  • Pieces of the Earth landed on Mars.

  • So clearly, those two planets may have been seeded by the same material.

  • So yeah, maybe Granddady is sitting there on the surface and waiting for us.

  • But that also means that we can go to Mars and try to find traces of our own origin.

  • Mars may hold that secret for us.

  • This is why Mars is so special to us.

  • But for that to happen,

  • Mars needed to be habitable at the time when conditions were right.

  • So was Mars habitable?

  • We have a number of missions telling us exactly the same thing today.

  • At the time when life appeared on the Earth,

  • Mars did have an ocean, it had volcanoes, it had lakes,

  • and it had deltas like the beautiful picture you see here.

  • This picture was sent by the Curiosity rover only a few weeks ago.

  • It shows the remnants of a delta, and this picture tells us something:

  • water was abundant

  • and stayed founting at the surface for a very long time.

  • This is good news for life.

  • Life chemistry takes a long time to actually happen.

  • So this is extremely good news,

  • but does that mean that if we go there, life will be easy to find on Mars?

  • Not necessarily.

  • Here's what happened:

  • At the time when life exploded at the surface of the Earth,

  • then everything went south for Mars,

  • literally.

  • The atmosphere was stripped away by solar winds,

  • Mars lost its magnetosphere,

  • and then cosmic rays and U.V. bombarded the surface

  • and water escaped to space and went underground.

  • So if we want to be able to understand,

  • if we want to be able to find those traces of the signatures of life

  • at the surface of Mars, if they are there,

  • we need to understand what was the impact of each of these events

  • on the preservation of its record.

  • Only then will we be able to know where those signatures are hiding,

  • and only then will we be able to send our rover to the right places

  • where we can sample those rocks that may be telling us something

  • really important about who we are,

  • or, if not, maybe telling us that somewhere, independently,

  • life has appeared on another planet.

  • So to do that, it's easy.

  • You only need to go back 3.5 billion years ago

  • in the past of a planet.

  • We just need a time machine.

  • Easy, right?

  • Well, actually, it is.

  • Look around you -- that's planet Earth.

  • This is our time machine.

  • Geologists are using it to go back in the past of our own planet.

  • I am using it a little bit differently.

  • I use planet Earth to go in very extreme environments

  • where conditions were similar to those of Mars

  • at the time when the climate changed,

  • and there I'm trying to understand what happened.

  • What are the signatures of life?

  • What is left? How are we going to find it?

  • So for one moment now I'm going to take you with me

  • on a trip into that time machine.

  • And now, what you see here, we are at 4,500 meters in the Andes,

  • but in fact we are less than a billion years after the Earth and Mars formed.

  • The Earth and Mars will have looked pretty much exactly like that --

  • volcanoes everywhere, evaporating lakes everywhere,

  • minerals, hot springs,

  • and then you see those mounds on the shore of those lakes?

  • Those are built by the descendants of the first organisms

  • that gave us the first fossil on Earth.

  • But if we want to understand what's going on, we need to go a little further.

  • And the other thing about those sites

  • is that exactly like on Mars three and a half billion years ago,

  • the climate is changing very fast, and water and ice are disappearing.

  • But we need to go back to that time when everything changed on Mars,

  • and to do that, we need to go higher.

  • Why is that?

  • Because when you go higher,

  • the atmosphere is getting thinner, it's getting more unstable,

  • the temperature is getting cooler, and you have a lot more U.V. radiation.

  • Basically,

  • you are getting to those conditions on Mars when everything changed.

  • So I was not promising anything about a leisurely trip on the time machine.

  • You are not going to be sitting in that time machine.

  • You have to haul 1,000 pounds of equipment to the summit

  • of this 20,000-foot volcano in the Andes here.

  • That's about 6,000 meters.

  • And you also have to sleep on 42-degree slopes

  • and really hope that there won't be any earthquake that night.

  • But when we get to the summit, we actually find the lake we came for.

  • At this altitude, this lake is experiencing exactly the same conditions

  • as those on Mars three and a half billion years ago.

  • And now we have to change our voyage

  • into an inner voyage inside that lake,

  • and to do that, we have to remove our mountain gear

  • and actually don suits and go for it.

  • But at the time we enter that lake, at the very moment we enter that lake,

  • we are stepping back

  • three and a half billion years in the past of another planet,

  • and then we are going to get the answer came for.

  • Life is everywhere, absolutely everywhere.

  • Everything you see in this picture is a living organism.

  • Maybe not so the diver, but everything else.

  • But this picture is very deceiving.

  • Life is abundant in those lakes,

  • but like in many places on Earth right now and due to climate change,

  • there is a huge loss in biodiversity.

  • In the samples that we took back home,

  • 36 percent of the bacteria in those lakes were composed of three species,

  • and those three species are the ones that have survived so far.

  • Here's another lake, right next to the first one.

  • The red color you see here is not due to minerals.

  • It's actually due to the presence of a tiny algae.

  • In this region, the U.V. radiation is really nasty.

  • Anywhere on Earth, 11 is considered to be extreme.

  • During U.V. storms there, the U.V. Index reaches 43.

  • SPF 30 is not going to do anything to you over there,

  • and the water is so transparent in those lakes

  • that the algae has nowhere to hide, really,

  • and so they are developing their own sunscreen,

  • and this is the red color you see.

  • But they can adapt only so far,

  • and then when all the water is gone from the surface,

  • microbes have only one solution left:

  • They go underground.

  • And those microbes, the rocks you see in that slide here,

  • well, they are actually living inside rocks

  • and they are using the protection of the translucence of the rocks

  • to get the good part of the U.V.

  • and discard the part that could actually damage their DNA.

  • And this is why we are taking our rover

  • to train them to search for life on Mars in these areas,

  • because if there was life on Mars three and a half billion years ago,

  • it had to use the same strategy to actually protect itself.

  • Now, it is pretty obvious

  • that going to extreme environments is helping us very much

  • for the exploration of Mars and to prepare missions.

  • So far, it has helped us to understand the geology of Mars.

  • It has helped to understand the past climate of Mars and its evolution,

  • but also its habitability potential.

  • Our most recent rover on Mars has discovered traces of organics.

  • Yeah, there are organics at the surface of Mars.

  • And it also discovered traces of methane.

  • And we don't know yet if the methane in question

  • is really from geology or biology.

  • Regardless, what we know is that because of the discovery,

  • the hypothesis that there is still life present on Mars today

  • remains a viable one.

  • So by now, I think I have convinced you that Mars is very special to us,

  • but it would be a mistake to think that Mars is the only place

  • in the solar system that is interesting to find potential microbial life.

  • And the reason is because Mars and the Earth

  • could have a common root to their tree of life,

  • but when you go beyond Mars, it's not that easy.

  • Celestial mechanics is not making it so easy