Translator: Amanda Chu Reviewer: Peter van de Ven
I'm an astronomer; I study stars and planets.
Astronomy, from its ancient roots,
has always been about stars, planets, galaxies -
the cosmos as a whole.
But what if I told you that the future of astronomy is biology?
Yes, biology.
Let's see why.
It is a part of the story
that has been building up over the past 20 years,
but in the last year, things have come to a head,
and I'm here to share some of them with you.
First, nine months ago, NASA launched a new space telescope.
We call it the TESS mission,
and it follows up on a previous space telescope,
the Kepler mission.
I'm honored to be on the teams of both of these missions.
And what happened
is the previous mission, the Kepler mission,
really brought a revolution to the field of astronomy.
It established beyond our expectations
that there're more planets in our galaxy and in the cosmos than stars.
It established
that there are more than 3,500 planets
that we can study right now,
and the number is growing,
but more importantly,
one historical result of the Kepler mission
was to show that every two out of ten stars in our galaxy
host a planet just like our own Earth.
Every two in ten stars!
This makes for a staggering number of one to ten billion Earths
in our Milky Way Galaxy.
So TESS is the next step.
And three weeks ago,
we showed the world our first tally of planets -
just a few to start with, but the number is quickly growing -
and in the next months and the next ten years,
you will see thousands more.
This whole new development in astronomy
has an overarching goal from the very beginning,
and that overarching goal
has been the search for alien life beyond the solar system,
the search for alien biology,
and TESS is the mission
that is going to provide the targets for this search.
So how do we achieve such a lofty goal, to find life on other distant planets?
The answer is spectroscopy.
It is our established way to use the remote sensing
to find those faint signals
of different gases in the atmospheres of very distant planets,
like the one we find around other stars,
the exoplanets.
In this particular case,
you see the specific gas that we are targeting now,
which is oxygen gas.
Learning from the history of life on our own planet Earth,
oxygen is a good marker.
But there is little less in our toolbox,
and that is a potential problem.
Because what if life on other planets didn't follow exactly the same history?
What if the biochemistry underlying life on other planets is slightly different?
These are quite possible cases. And are we prepared for them?
This is when our team got together and started working in the lab.
It is a team consisting of several collaborating labs,
trying to build a chemical system that functions like life,
like a living cell -
we call it "the minimal protocell project" -
and we know that this living system
will have to consist of three basic subsystems,
each of them corresponding to a specific molecule
with the names that you see written there.
In addition, those molecules will not have to just self-assemble there,
they will have to be able to self-assemble, self-repair
and, finally, self-reproduce
like life as we know it and life as we expect it
so that it can propagate and sustain itself;
thus, we focused our attention on one of those specific molecules
which is called RNA,
the cousin of the well-known DNA molecule.
Each one of us, from virus to elephants, every living thing on Earth, has RNA.
And so what we are trying to achieve
is to understand the self-assembly of RNA, surrounded by a membrane,
which self-assembles around it,
and then, because we know RNA is both a genetic molecule -
like DNA, it carries the information for future copies of this living cell -
as well as has biological function that allows it to make a copy of itself
without outside help.
DNA cannot do that.
RNA is an ideal example of what we call the Initial RNA World Hypothesis.
We also knew that RNA can assemble itself readily,
provided there is some UV light in the system,
and that was established almost ten years ago
by John Sutherland in England.
So RNA, like DNA, is a chain molecule.
It consists of individual identical units - four of them -
which line up in a string,
and if you provided UV light to that system,
it will do so by its own devices,
using the energy coming out from the UV light.
So the first thing we did with that knowledge,
we try to understand that curious need for UV light.
We knew it needed energy, but the question was,
What exactly was the UV light that was needed?
And the first thing we found
is that it was a very specific UV light that was necessary.
So let's see if you know your UV light.
You, of course, have to
because you have to be careful, especially in the summer -
sunblock and sunglasses.
Perhaps some of you read the fine print
and already know about UVA, UVB and UVC light.
Well, what we found is that the self-assembly of RNA,
and now a father of those three basic subsystem molecules,
requires UVC light - specifically UVC light.
The second thing which we found
is that UVC light reaches the surface of the early Earth.
We could tell that from the geological record
and being able to see that.
Now we have gone one step further
and expect that other earth-like planets
will also allow UVC light to reach the surface
in the amounts that are necessary to self-assemble the building blocks.
So in the lab,
we have been able to see this self-assembly
in one of our collaborator labs, the Szostak Lab -
You see here RNA assembling and growing -
that is the green stuff in the red membrane vesicles,
the little bubbles that look like protocells growing inside,
being built from individual units
that are being synthesized simultaneously outside of the cells.
And so we can put a check mark on the first step:
we now understand and can see in the lab
self-assembly of all the necessary building blocks.
But we have two more to go.
And if you are going to get to the self-producing,
which will be necessary, ultimately, for this to be like a living cell,
we have to be able to sustain those little chains of RNA
and other molecules long enough,
and for that, we need to understand the function of self-repair.
Self-repair is very common to life.
In fact, it's a defining property,
both at the level of sophisticated organisms like us -
all of you know that when you cut yourself,
the wound eventually heals -
but this is a process that goes all the way to the cell itself
and then to individual cells and individual molecules.
But what is the concept of self-repair for an individual molecule?
For this, you have to go to the lab
and use equipment which is somewhat sophisticated and modern.
On one hand are the boxes
which reproduce the light that comes from the early sun or other stars,
and this is the UVC light that we talked about.
On the right-hand side
is where we have the sample which simulates the planet conditions,
the conditions on the surface of the planet.
In addition,
this equipment allows us to see the molecules in their natural habitat,
which means at their natural time scales -
the daily routine, if you will, of individual molecules.
Molecules are extremely small - they're the size of just a few atoms -
hence, their daily routine
takes a lot shorter time than a full day for us -
a lot shorter time.
So that's why just in a few seconds,
I reproduce the entire history of our big universe -
I call this system a "universe in a box." (Laughter)
And so what can I do with it?
Well, it turns out
I can see the molecule in their daily chores
by looking at their fingerprints -
remember spectroscopy? Each molecule has very specific fingerprints -
but this time, I watch them over time,
over the entire day, even years, and billions of years
in the sense of the molecule,
except that billions of 10 billion years for a molecule is just one second,
in fact, less than one second,
and hence the "universe in a box" here.
But what is more important and what happened for the first time?
It will realize
that the synthesis and the creation of the building blocks of life
can be reproduced in the lab over a period of seconds, minutes, a day,
as opposed to the old idea that maybe this process took millions of years.
No, we can see what's happening in seconds.
If we know how to look and if we look fast enough,
then we can see what happens to a molecule.
And what we found out was a very profound insight:
It is the chemistry that produces these hundreds and thousands of molecules,
but just a few of them are selected,
the others are eliminated by the UV light -
they're destroyed -
because only a few of the molecules are stable to both be synthesized
and especially, to survive and self-repair in the process.
Guess which are these molecules?
They're the same ones which are still in our bodies,
the RNA, the DNA, the amino acids -
just the twenty one that are stable,
all the others are not, and they go just like the marble
with the remaining sculpture in the middle.
And so, for the first time, we started understanding
how a chain, like the chain of RNA, with individual units stacked -
we call it base stacking -
would be damaged by the UV light,
which was a paradox -
you need UV light to produce it,
but it damages you because it produces this red current of electricity
when the UV light hits you.
It's actually able to self-repair
because it's able to fold and make a double helix.
It is that folding - the base pairing as we call it -
that leads to the repair and the unique property of the molecules
that actually end up building life.
So where are we?
We now have checked both self-assembly and self-repair,
understood the UV light paradox,
that you need UV light, but it destroys life, yes,
but it only destroys the bad molecules and leaves the ones that are here today.
The next, final, step, self-reproduction,
under these conditions is a formidable task,
but it's now near at hand
because the self-repair was the necessary step to get to this.
So now we can summarize what we have learned.
And what we have learned
is profound from the point of view
of building the life in the lab,
but what good is that to the astronomer?
So let's go back
and look at this statement with the eyes of the astronomer.
And if you do that, you will see in this statement
a map with clues which tell you the path to what you're seeking.
The first one, born of stellar UV light,
tells you that you have to look for stars which produce enough UVC lights,
and not all of them do,
so you have to find rocky planets orbiting those kind of stars.
The second thing is that the planet itself
has to be allowing just the right amount of UVC light to the surface,
so carbon dioxide is okay in the atmosphere,
but too much sulfur will block it.
So what has happened
is we have managed to narrow down the search
for the planets that we are going to study
once TESS provides us
with those new planets close to us that we can do spectroscopy on.
And because we know from Kepler that there's so many of them,
the future is very bright for this search.
The most amazing part of it
is that we live in a time when within our lifetimes,
we'll be able to answer - at least try to answer -
the biggest question:
Are we alone in the universe?
I think we are lucky to be alive.
Thank you.
(Applause)