1
00:00:01,333 --> 00:00:04,786
So I'm pretty sure that I'm not
the only one in this room

2
00:00:04,810 --> 00:00:09,522
who at some point have found myself,
you know, looking up towards the stars,

3
00:00:09,546 --> 00:00:12,180
and wondered, you know, "Are we it,

4
00:00:12,204 --> 00:00:16,005
or are there other living planets
out there such as our own?"

5
00:00:17,014 --> 00:00:20,521
I guess it is possible
that I'm then the only person

6
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who has obsessed enough
about that question

7
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to make it my career.

8
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But moving on.

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00:00:26,506 --> 00:00:29,617
How do we get to this question?

10
00:00:29,641 --> 00:00:32,008
Well, I would argue the first thing to do

11
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is to turn our eyes back down from the sky
to our own planet, the Earth.

12
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And think about just how lucky
did the Earth have to be

13
00:00:42,404 --> 00:00:44,626
to be the living planet it is.

14
00:00:44,650 --> 00:00:46,895
Well, it had to be
at least somewhat lucky.

15
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Had we been sitting closer to the Sun

16
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or a bit further away,

17
00:00:51,482 --> 00:00:55,998
any water that we have had
would have boiled off or frozen over.

18
00:00:56,022 --> 00:01:00,083
And I mean, it's not a given
that a planet has water on it.

19
00:01:00,107 --> 00:01:03,725
So had we been a dry planet,

20
00:01:03,749 --> 00:01:06,083
there would not have been
a lot of life on it.

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00:01:06,107 --> 00:01:09,664
And even if we had had all the water
that we have today,

22
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if that water had not been accompanied

23
00:01:11,958 --> 00:01:15,069
by the right kind of chemicals
to get life going,

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we would have a wet planet,
but just as dead.

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So it's so many things that can go wrong,

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what are the chances that they go right?

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What are the chances that the planet forms

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with at least the basic ingredients needed

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to have an origins of life happening?

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Well, let's explore that together.

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00:01:35,190 --> 00:01:37,237
So if you're going to have
a living planet,

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00:01:37,261 --> 00:01:40,667
the first thing you're going to need

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00:01:40,691 --> 00:01:42,483
is a planet.

34
00:01:42,507 --> 00:01:43,508
(Laughter)

35
00:01:43,532 --> 00:01:45,656
But not any planet will do.

36
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You're probably going to need
a rather specific and earthlike planet.

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00:01:49,482 --> 00:01:50,974
A planet that is rocky,

38
00:01:50,998 --> 00:01:53,106
so you can have both oceans and land,

39
00:01:53,130 --> 00:01:57,362
and it's sitting neither too close
nor too far away from its star,

40
00:01:57,386 --> 00:01:59,838
but at the just-right temperature.

41
00:01:59,862 --> 00:02:03,157
And it's just right
for liquid water, that is.

42
00:02:03,181 --> 00:02:06,276
So how many of these planets
do we have in our galaxy?

43
00:02:06,800 --> 00:02:10,268
Well, one of the great discoveries
of the past decades

44
00:02:10,292 --> 00:02:12,772
is that planets are incredibly common.

45
00:02:13,212 --> 00:02:16,212
Almost every star
has a planet around them.

46
00:02:16,236 --> 00:02:17,649
Some have many.

47
00:02:17,673 --> 00:02:20,562
And among these planets,

48
00:02:20,586 --> 00:02:24,426
on the order of a few percent
are earthlike enough

49
00:02:24,450 --> 00:02:28,006
that we would consider them
potentially living planets.

50
00:02:28,030 --> 00:02:31,665
So having the right kind of planet
is actually not that difficult

51
00:02:31,689 --> 00:02:35,927
when we consider that there's
about 100 billion stars in our galaxy.

52
00:02:35,951 --> 00:02:40,046
So that gives you about a billion
potential living planets.

53
00:02:40,427 --> 00:02:43,013
But it's not enough to just be
at the right temperature

54
00:02:43,037 --> 00:02:44,847
or have the right overall composition.

55
00:02:44,871 --> 00:02:47,138
You also need the right chemicals.

56
00:02:47,553 --> 00:02:51,768
And what the second and important
ingredient to make a living planet is --

57
00:02:51,792 --> 00:02:54,720
I think it's pretty intuitive --

58
00:02:54,744 --> 00:02:56,331
it's water.

59
00:02:56,355 --> 00:03:01,498
After all, we did define our planet
as being potentially living

60
00:03:01,522 --> 00:03:04,202
if it had the right temperature
to keep water liquid.

61
00:03:04,838 --> 00:03:08,409
And I mean, here on Earth,
life is water-based.

62
00:03:08,711 --> 00:03:10,005
But more generally,

63
00:03:10,029 --> 00:03:14,283
water is just really good
as a meeting place for chemicals.

64
00:03:14,307 --> 00:03:16,307
It is a very special liquid.

65
00:03:16,331 --> 00:03:19,911
So this is our second basic ingredient.

66
00:03:20,276 --> 00:03:22,208
Now the third ingredient, I think,

67
00:03:22,232 --> 00:03:24,847
is probably a little bit more surprising.

68
00:03:24,871 --> 00:03:27,656
I mean, we are going to need
some organics in there,

69
00:03:27,680 --> 00:03:29,814
since we are thinking about organic life.

70
00:03:30,188 --> 00:03:31,902
But the organic molecule

71
00:03:31,926 --> 00:03:35,705
that seems to be at the center
of the chemical networks

72
00:03:35,729 --> 00:03:40,155
that can produce biomolecules
is hydrogen cyanide.

73
00:03:40,481 --> 00:03:43,814
So for those of you who know
what this molecule is like,

74
00:03:43,838 --> 00:03:47,219
you know it's something
that it's a good idea to stay away from.

75
00:03:47,776 --> 00:03:48,927
But it turns out

76
00:03:48,951 --> 00:03:52,117
that what's really, really bad
for advanced life forms,

77
00:03:52,141 --> 00:03:53,799
such as yourselves,

78
00:03:53,823 --> 00:03:57,307
is really, really good
to get the chemistry started,

79
00:03:57,331 --> 00:04:00,616
the right kind of chemistry
that can lead to origins of life.

80
00:04:01,180 --> 00:04:03,983
So now we have our three
ingredients that we need,

81
00:04:04,007 --> 00:04:06,007
you know, the temperate planet,

82
00:04:06,031 --> 00:04:08,579
water and hydrogen cyanide.

83
00:04:08,603 --> 00:04:11,372
So how often do these three come together?

84
00:04:11,396 --> 00:04:14,045
How many temperate planets
are there out there

85
00:04:14,069 --> 00:04:16,536
that have water and hydrogen cyanide?

86
00:04:17,030 --> 00:04:18,688
Well, in an ideal world,

87
00:04:18,712 --> 00:04:24,688
we would now turn one of our telescopes
towards one of these temperate planets

88
00:04:24,712 --> 00:04:26,275
and check for ourselves.

89
00:04:26,299 --> 00:04:29,933
Just, "Do these planets have water
and cyanides on them?"

90
00:04:30,529 --> 00:04:36,663
Unfortunately, we don't yet
have large enough telescopes to do this.

91
00:04:36,687 --> 00:04:40,569
We can detect molecules
in the atmospheres of some planets.

92
00:04:40,593 --> 00:04:42,196
But these are large planets

93
00:04:42,220 --> 00:04:44,680
sitting often pretty close to their star,

94
00:04:44,704 --> 00:04:47,490
nothing like these, you know,
just-right planets

95
00:04:47,514 --> 00:04:48,980
that we're talking about here,

96
00:04:49,004 --> 00:04:51,196
which are much smaller and further away.

97
00:04:51,530 --> 00:04:53,704
So we have to come up with another way.

98
00:04:53,728 --> 00:04:58,662
And the other way that we have
conceived of and then followed

99
00:04:58,686 --> 00:05:01,305
is to instead of looking
for these molecules

100
00:05:01,329 --> 00:05:03,519
in the planets when they exist,

101
00:05:03,543 --> 00:05:07,283
is to look for them in the material
that's forming new planets.

102
00:05:07,307 --> 00:05:11,752
So planets form in discs
of dust and gas around young stars.

103
00:05:11,776 --> 00:05:15,895
And these discs get their material
from the interstellar medium.

104
00:05:15,919 --> 00:05:18,633
Turns out that the empty space
you see between stars

105
00:05:18,657 --> 00:05:22,391
when you are looking up towards them,
asking existential questions,

106
00:05:22,415 --> 00:05:24,590
is not as empty as it seems,

107
00:05:24,614 --> 00:05:26,574
but actually full of gas and dust,

108
00:05:26,598 --> 00:05:28,844
which can, you know,
come together in clouds,

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00:05:28,868 --> 00:05:32,223
then collapses to form these discs,
stars and planets.

110
00:05:32,967 --> 00:05:37,538
And one of the things we always see
when we do look at these clouds

111
00:05:37,562 --> 00:05:38,967
is water.

112
00:05:38,991 --> 00:05:41,665
You know, I think we have a tendency
to think about water

113
00:05:41,689 --> 00:05:44,289
as something that's,
you know, special to us.

114
00:05:44,852 --> 00:05:48,661
Water is one of the most abundant
molecules in the universe,

115
00:05:48,685 --> 00:05:50,410
including in these clouds,

116
00:05:50,434 --> 00:05:52,901
these star- and planet-forming clouds.

117
00:05:53,661 --> 00:05:54,815
And not only that --

118
00:05:54,839 --> 00:05:56,815
water is also a pretty robust molecule:

119
00:05:56,839 --> 00:05:59,236
it's actually not that easy to destroy.

120
00:05:59,260 --> 00:06:02,339
So a lot of this water
that is in interstellar medium

121
00:06:02,363 --> 00:06:07,950
will survive the rather dangerous,
collapsed journey from clouds

122
00:06:07,974 --> 00:06:10,156
to disc, to planet.

123
00:06:10,967 --> 00:06:13,046
So water is alright.

124
00:06:13,070 --> 00:06:15,927
That second ingredient
is not going to be a problem.

125
00:06:15,951 --> 00:06:20,173
Most planets are going to form
with some access to water.

126
00:06:21,125 --> 00:06:23,458
So what about hydrogen cyanide?

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00:06:23,482 --> 00:06:27,990
Well, we also see cyanides
and other similar organic molecules

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00:06:28,014 --> 00:06:30,601
in these interstellar clouds.

129
00:06:30,625 --> 00:06:35,910
But here, we're less certain
about the molecules surviving,

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00:06:35,934 --> 00:06:37,942
going from the cloud to the disc.

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00:06:37,966 --> 00:06:40,633
They're just a bit more delicate,
a bit more fragile.

132
00:06:40,657 --> 00:06:43,992
So if we're going to know
that this hydrogen cyanide

133
00:06:44,016 --> 00:06:47,222
is sitting in the vicinity
of new planets forming,

134
00:06:47,246 --> 00:06:49,540
we'd really need to see it
in the disc itself,

135
00:06:49,564 --> 00:06:51,794
in these planet-forming discs.

136
00:06:51,818 --> 00:06:54,260
So about a decade ago,

137
00:06:54,284 --> 00:06:59,522
I started a program
to look for this hydrogen cyanide

138
00:06:59,546 --> 00:07:02,722
and other molecules
in these planet-forming discs.

139
00:07:02,746 --> 00:07:05,983
And this is what we found.

140
00:07:06,007 --> 00:07:08,928
So good news, in these six images,

141
00:07:08,952 --> 00:07:15,069
those bright pixels represent emissions
originating from hydrogen cyanide

142
00:07:15,093 --> 00:07:18,577
in planet-forming discs
hundreds of light-years away

143
00:07:18,601 --> 00:07:20,625
that have made it to our telescope,

144
00:07:20,649 --> 00:07:21,926
onto the detector,

145
00:07:21,950 --> 00:07:24,684
allowing us to see it like this.

146
00:07:25,228 --> 00:07:26,506
So the very good news

147
00:07:26,530 --> 00:07:30,601
is that these discs do indeed have
hydrogen cyanide in them.

148
00:07:30,625 --> 00:07:34,024
That last, more elusive ingredient.

149
00:07:35,159 --> 00:07:40,215
Now the bad news is that we don't know
where in the disc it is.

150
00:07:40,810 --> 00:07:42,207
If we look at these,

151
00:07:42,231 --> 00:07:44,530
I mean, no one can say
they are beautiful images,

152
00:07:44,554 --> 00:07:47,316
even at the time when we got them.

153
00:07:47,340 --> 00:07:50,760
You see the pixel size is pretty big

154
00:07:50,784 --> 00:07:53,911
and it's actually bigger
than these discs themselves.

155
00:07:53,935 --> 00:07:55,391
So each pixel here

156
00:07:55,415 --> 00:07:58,895
represents something that's much bigger
than our solar system.

157
00:07:59,345 --> 00:08:01,276
And that means

158
00:08:01,300 --> 00:08:05,410
that we don't know where in the disc
the hydrogen cyanide is coming from.

159
00:08:05,768 --> 00:08:06,998
And that's a problem,

160
00:08:07,022 --> 00:08:08,571
because these temperate planets,

161
00:08:08,595 --> 00:08:11,553
they can't access
hydrogen cyanide just anywhere,

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00:08:11,577 --> 00:08:14,954
but it must be fairly close
to where they assemble

163
00:08:14,978 --> 00:08:16,868
for them to have access to it.

164
00:08:16,892 --> 00:08:22,034
So to bring this home,
let's think about an analogous example,

165
00:08:22,058 --> 00:08:25,280
that is, of cypress growing
in the United States.

166
00:08:25,661 --> 00:08:27,371
So let's say, hypothetically,

167
00:08:27,395 --> 00:08:29,166
that you've returned from Europe

168
00:08:29,190 --> 00:08:31,934
where you have seen
beautiful Italian cypresses,

169
00:08:31,958 --> 00:08:34,371
and you want to understand, you know,

170
00:08:34,395 --> 00:08:37,014
does it make sense to import them
to the United States.

171
00:08:37,038 --> 00:08:38,672
Could you grow them here?

172
00:08:38,696 --> 00:08:40,760
So you talk to the cypress experts,

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00:08:40,784 --> 00:08:42,448
they tell you that there is indeed

174
00:08:42,472 --> 00:08:46,410
a band of not-too-hot, not-too-cold
across the United States

175
00:08:46,434 --> 00:08:47,974
where you could grow them.

176
00:08:47,998 --> 00:08:51,896
And if you have a nice,
high-resolution map or image like this,

177
00:08:51,920 --> 00:08:54,745
it's quite easy to see
that this cypress strip

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00:08:54,769 --> 00:08:58,229
overlaps with a lot of green
fertile land pixels.

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00:08:58,753 --> 00:09:01,720
Even if I start degrading
this map quite a bit,

180
00:09:01,744 --> 00:09:04,053
making it lower and lower resolution,

181
00:09:04,077 --> 00:09:05,409
it's still possible to tell

182
00:09:05,433 --> 00:09:09,027
that there's going to be some fertile land
overlapping with this strip.

183
00:09:09,466 --> 00:09:14,497
But what about if the whole United States

184
00:09:14,521 --> 00:09:17,727
is incorporated into a single pixel?

185
00:09:17,751 --> 00:09:19,768
If the resolution is that low.

186
00:09:19,792 --> 00:09:21,085
What do you do now,

187
00:09:21,109 --> 00:09:26,231
how do you now tell whether you can grow
cypresses in the United States?

188
00:09:26,538 --> 00:09:28,466
Well the answer is you can't.

189
00:09:28,490 --> 00:09:30,878
I mean, there's definitely
some fertile land there,

190
00:09:30,902 --> 00:09:33,656
or you wouldn't have
that green tint to the pixel,

191
00:09:33,680 --> 00:09:35,649
but there's just no way of telling

192
00:09:35,673 --> 00:09:38,871
whether any of that green
is in the right place.

193
00:09:38,895 --> 00:09:41,663
And that is exactly the problem
we were facing

194
00:09:41,687 --> 00:09:44,879
with our single-pixel
images of these discs

195
00:09:44,903 --> 00:09:46,498
with hydrogen cyanide.

196
00:09:46,522 --> 00:09:48,696
So what we need is something analogous,

197
00:09:48,720 --> 00:09:51,791
at least those low-resolution maps
that I just showed you,

198
00:09:51,815 --> 00:09:56,664
to be able to tell whether there's overlap
between where the hydrogen cyanide is

199
00:09:56,688 --> 00:09:59,648
and where these planets
can access it as they are forming.

200
00:10:00,236 --> 00:10:03,439
So coming to the rescue, a few years ago,

201
00:10:03,463 --> 00:10:07,447
is this new, amazing,
beautiful telescope ALMA,

202
00:10:07,471 --> 00:10:10,328
the Atacama Large Millimeter
and submillimeter Array

203
00:10:10,352 --> 00:10:11,552
in northern Chile.

204
00:10:11,900 --> 00:10:15,663
So, ALMA is amazing
in many different ways,

205
00:10:15,687 --> 00:10:18,171
but the one that I'm going to focus on

206
00:10:18,195 --> 00:10:22,116
is that, as you can see,
I call this one telescope,

207
00:10:22,140 --> 00:10:25,475
but you can there are actually
many dishes in this image.

208
00:10:25,499 --> 00:10:30,126
And this is a telescope
that consists of 66 individual dishes

209
00:10:30,150 --> 00:10:31,750
that all work in unison.

210
00:10:32,483 --> 00:10:35,046
And that means that you have a telescope

211
00:10:35,070 --> 00:10:39,937
that is the size of the largest distance
that you can put these dishes

212
00:10:39,961 --> 00:10:41,278
away from one another.

213
00:10:41,302 --> 00:10:44,405
Which in ALMA's case are a few miles.

214
00:10:44,429 --> 00:10:47,897
So you have a more
than mile-sized telescope.

215
00:10:48,267 --> 00:10:50,140
And when you have such a big telescope,

216
00:10:50,164 --> 00:10:52,665
you can zoom in on really small things,

217
00:10:52,689 --> 00:10:57,561
including making maps of hydrogen cyanide
in these planet-forming discs.

218
00:10:57,585 --> 00:11:00,410
So when ALMA came online a few years ago,

219
00:11:00,434 --> 00:11:04,507
that was one of the first things
that I proposed that we use it for.

220
00:11:05,086 --> 00:11:09,022
And what does a map of hydrogen cyanide
look like in a disc?

221
00:11:09,046 --> 00:11:11,560
Is the hydrogen cyanide
at the right place?

222
00:11:11,584 --> 00:11:13,695
And the answer is that it is.

223
00:11:13,719 --> 00:11:15,726
So this is the map.

224
00:11:15,750 --> 00:11:19,694
You see the hydrogen cyanide emission
being spread out across the disc.

225
00:11:19,718 --> 00:11:21,568
First of all, it's almost everywhere,

226
00:11:21,592 --> 00:11:23,155
which is very good news.

227
00:11:23,179 --> 00:11:26,364
But you have a lot
of extra bright emission

228
00:11:26,388 --> 00:11:29,591
coming from close to the star
towards the center of the disc.

229
00:11:29,965 --> 00:11:33,125
And this is exactly
where we want to see it.

230
00:11:33,149 --> 00:11:35,791
This is close to where
these planets are forming.

231
00:11:35,815 --> 00:11:39,601
And this is not what we see
just towards one disc --

232
00:11:39,625 --> 00:11:41,982
here are three more examples.

233
00:11:42,006 --> 00:11:44,089
You can see they all show
the same thing --

234
00:11:44,113 --> 00:11:46,577
lots of bright hydrogen cyanide emission

235
00:11:46,601 --> 00:11:48,926
coming from close
to the center of the star.

236
00:11:49,228 --> 00:11:51,910
For full disclosure,
we don't always see this.

237
00:11:51,934 --> 00:11:54,466
There are discs where we see the opposite,

238
00:11:54,490 --> 00:11:57,712
where there's actually a hole
in the emission towards the center.

239
00:11:57,736 --> 00:12:00,276
So this is the opposite
of what we want to see, right?

240
00:12:00,300 --> 00:12:02,458
This is not places where we could research

241
00:12:02,482 --> 00:12:06,490
if there is any hydrogen cyanide around
where these planets are forming.

242
00:12:06,514 --> 00:12:08,093
But in most cases,

243
00:12:08,117 --> 00:12:10,125
we just don't detect hydrogen cyanide,

244
00:12:10,149 --> 00:12:12,549
but we detect it in the right place.

245
00:12:13,038 --> 00:12:15,077
So what does all this mean?

246
00:12:15,101 --> 00:12:17,547
Well, I told you in the beginning

247
00:12:17,571 --> 00:12:20,958
that we have lots
of these temperate planets,

248
00:12:20,982 --> 00:12:22,887
maybe a billion or so of them,

249
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that could have life develop on them

250
00:12:25,457 --> 00:12:27,981
if they have the right ingredients.

251
00:12:28,005 --> 00:12:29,179
And I've also shown

252
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that we think a lot of the time,
the right ingredients are there --

253
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we have water, we have hydrogen cyanide,

254
00:12:35,305 --> 00:12:37,506
there will be other
organic molecules as well

255
00:12:37,530 --> 00:12:39,197
coming with the cyanides.

256
00:12:39,879 --> 00:12:44,101
This means that planets
with the most basic ingredients for life

257
00:12:44,125 --> 00:12:47,148
are likely to be incredibly
common in our galaxy.

258
00:12:48,133 --> 00:12:50,688
And if all it takes for life to develop

259
00:12:50,712 --> 00:12:54,014
is to have these basic
ingredients available,

260
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there should be a lot
of living planets out there.

261
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But that is of course a big if.

262
00:12:59,361 --> 00:13:02,313
And I would say the challenge
of the next decades,

263
00:13:02,337 --> 00:13:04,821
for both astronomy and chemistry,

264
00:13:04,845 --> 00:13:07,585
is to figure out just how often

265
00:13:07,609 --> 00:13:10,363
we go from having
a potentially living planet

266
00:13:10,387 --> 00:13:12,791
to having an actually living one.

267
00:13:12,815 --> 00:13:13,966
Thank you.

268
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(Applause)