1
00:00:03,909 --> 00:00:02,629
hi everyone i'm vicki meadows i'm a

2
00:00:05,670 --> 00:00:03,919
professor of astronomy

3
00:00:07,269 --> 00:00:05,680
at the university of washington and the

4
00:00:08,470 --> 00:00:07,279
director of the astrobiology program

5
00:00:10,070 --> 00:00:08,480
there

6
00:00:11,910 --> 00:00:10,080
um and in this presentation i'm going to

7
00:00:13,430 --> 00:00:11,920
provide an overview of the claimed

8
00:00:15,270 --> 00:00:13,440
discovery of phosphine

9
00:00:16,630 --> 00:00:15,280
a potential biosignature in the venus

10
00:00:17,830 --> 00:00:16,640
atmosphere

11
00:00:19,590 --> 00:00:17,840
and also look at the subsequent

12
00:00:21,269 --> 00:00:19,600
community response to attempt to

13
00:00:22,950 --> 00:00:21,279
validate and increase our confidence in

14
00:00:26,710 --> 00:00:22,960
this discovery

15
00:00:28,950 --> 00:00:26,720
september 2020 and so it's fairly recent

16
00:00:30,950 --> 00:00:28,960
but it's provided a great example of how

17
00:00:32,950 --> 00:00:30,960
we as a community respond to a bicycle

18
00:00:34,709 --> 00:00:32,960
detection claim

19
00:00:36,790 --> 00:00:34,719
it's also an interesting test case for

20
00:00:39,590 --> 00:00:36,800
exoplanet biasing detection

21
00:00:41,430 --> 00:00:39,600
which will also necessarily be done via

22
00:00:43,190 --> 00:00:41,440
spectroscopy

23
00:00:44,229 --> 00:00:43,200
and whether or not you are convinced

24
00:00:45,750 --> 00:00:44,239
that there is phosphine in the

25
00:00:46,709 --> 00:00:45,760
atmosphere of venus and that is a sign

26
00:00:48,389 --> 00:00:46,719
of life

27
00:00:50,389 --> 00:00:48,399
the process of trying to verify the

28
00:00:51,670 --> 00:00:50,399
phosphene detection and interpretation

29
00:00:54,150 --> 00:00:51,680
is an important one

30
00:00:55,670 --> 00:00:54,160
that can help us think more deeply about

31
00:00:59,990 --> 00:00:55,680
how we might develop standards of

32
00:01:03,510 --> 00:01:01,910
so the phosphate and venus story starts

33
00:01:07,350 --> 00:01:03,520
with this paper

34
00:01:10,149 --> 00:01:07,360
led by jane grieves and team which

35
00:01:12,630 --> 00:01:10,159
showed detection of a line in the

36
00:01:14,550 --> 00:01:12,640
millimeter wave attributed to phosphine

37
00:01:15,670 --> 00:01:14,560
taken from both the james maxwell

38
00:01:17,590 --> 00:01:15,680
telescope and

39
00:01:20,630 --> 00:01:17,600
the atacama large millimeter array

40
00:01:22,710 --> 00:01:20,640
telescope on two separate occasions

41
00:01:25,270 --> 00:01:22,720
um in the paper not only the discovery

42
00:01:28,390 --> 00:01:25,280
of line is shown but also an exhaustive

43
00:01:30,069 --> 00:01:28,400
study of different ways that the

44
00:01:31,429 --> 00:01:30,079
phosphine might potentially be

45
00:01:33,749 --> 00:01:31,439
abiotically produced

46
00:01:34,950 --> 00:01:33,759
in the venus's atmosphere cloud surface

47
00:01:37,109 --> 00:01:34,960
subsurface

48
00:01:37,990 --> 00:01:37,119
or from lightning volcanic or immediate

49
00:01:40,630 --> 00:01:38,000
delivery

50
00:01:41,510 --> 00:01:40,640
is undertaken um and the conclusion is

51
00:01:43,030 --> 00:01:41,520
that there is no

52
00:01:45,590 --> 00:01:43,040
obvious way that phosphine could be

53
00:01:47,350 --> 00:01:45,600
produced via these processes

54
00:01:49,270 --> 00:01:47,360
so phosphine is believed then to

55
00:01:50,389 --> 00:01:49,280
originate from unknown photochemistry or

56
00:01:52,310 --> 00:01:50,399
geochemistry

57
00:01:53,670 --> 00:01:52,320
or by analogy with biological production

58
00:01:58,630 --> 00:01:53,680
of phosphine of earth

59
00:02:02,789 --> 00:02:01,590
so these are the discovery data the jcmt

60
00:02:04,950 --> 00:02:02,799
data is shown here

61
00:02:07,429 --> 00:02:04,960
in the second panel with the fit that

62
00:02:10,150 --> 00:02:07,439
shows 20 parts per billion of phosphine

63
00:02:11,830 --> 00:02:10,160
retrieved over here the armor narrow

64
00:02:12,550 --> 00:02:11,840
band shows an even more significant

65
00:02:19,510 --> 00:02:12,560
detection

66
00:02:21,510 --> 00:02:19,520
frequency note that the armor data were

67
00:02:22,949 --> 00:02:21,520
not used for abundance determinations

68
00:02:24,869 --> 00:02:22,959
because they were taken with an

69
00:02:26,790 --> 00:02:24,879
interferometric telescope the armor is

70
00:02:28,630 --> 00:02:26,800
an interferometric array

71
00:02:30,470 --> 00:02:28,640
um and that suffers from something

72
00:02:32,390 --> 00:02:30,480
called line dilution which makes the

73
00:02:34,070 --> 00:02:32,400
array actually less sensitive to things

74
00:02:35,270 --> 00:02:34,080
that are evenly spatially distributed

75
00:02:37,990 --> 00:02:35,280
across the disk

76
00:02:38,949 --> 00:02:38,000
and so the jcmt being a single dish uh

77
00:02:42,390 --> 00:02:38,959
was the

78
00:02:43,830 --> 00:02:42,400
observation um used to measure the

79
00:02:45,350 --> 00:02:43,840
actual abundance in this

80
00:02:47,350 --> 00:02:45,360
case here 20 parts per billion of

81
00:02:49,030 --> 00:02:47,360
phosphine and radiative and

82
00:02:49,990 --> 00:02:49,040
photochemical calculations suggested

83
00:02:51,830 --> 00:02:50,000
that this absorption

84
00:02:54,309 --> 00:02:51,840
actually came from within the clouds of

85
00:02:59,830 --> 00:02:56,790
but there is a complication because even

86
00:03:00,710 --> 00:02:59,840
though phosphine does absorb at 266.94

87
00:03:03,910 --> 00:03:00,720
gigahertz

88
00:03:06,070 --> 00:03:03,920
so does sulfur dioxide and so at the

89
00:03:07,270 --> 00:03:06,080
position at which the line was observed

90
00:03:09,509 --> 00:03:07,280
there was the potential for

91
00:03:11,110 --> 00:03:09,519
contamination from sulfur dioxide which

92
00:03:13,830 --> 00:03:11,120
is the third most common gas

93
00:03:16,229 --> 00:03:13,840
in the greenhouse in the in the venous

94
00:03:18,470 --> 00:03:16,239
atmosphere

95
00:03:19,589 --> 00:03:18,480
so the observers um knowing this set up

96
00:03:21,589 --> 00:03:19,599
a contamination

97
00:03:24,229 --> 00:03:21,599
test where they observed a sulfur

98
00:03:25,190 --> 00:03:24,239
dioxide reference line at 267.54

99
00:03:28,390 --> 00:03:25,200
gigahertz

100
00:03:28,949 --> 00:03:28,400
which is a clean so2 line um at that

101
00:03:31,430 --> 00:03:28,959
position

102
00:03:33,430 --> 00:03:31,440
they observed no sign of absorption so

103
00:03:34,869 --> 00:03:33,440
they failed to detect so2 at the

104
00:03:36,630 --> 00:03:34,879
reference position

105
00:03:39,509 --> 00:03:36,640
they then used that to set an upper

106
00:03:42,309 --> 00:03:39,519
limit on how much so2 could be there

107
00:03:44,070 --> 00:03:42,319
they then modeled the amount of so2 in

108
00:03:45,670 --> 00:03:44,080
that upper limit in this case 10 parts

109
00:03:48,949 --> 00:03:45,680
per billion of so2

110
00:03:50,550 --> 00:03:48,959
at the discovery wavelength and show

111
00:03:52,390 --> 00:03:50,560
that the so2 component

112
00:03:53,990 --> 00:03:52,400
would be extremely small and that the

113
00:03:56,229 --> 00:03:54,000
remainder of the absorption

114
00:04:00,550 --> 00:03:56,239
at the discovery wavelength would be due

115
00:04:02,550 --> 00:04:00,560
in fact to phosphine so obviously this

116
00:04:03,990 --> 00:04:02,560
was an extremely exciting discovery

117
00:04:05,750 --> 00:04:04,000
which caused a lot of interest

118
00:04:08,470 --> 00:04:05,760
especially in the community

119
00:04:09,030 --> 00:04:08,480
um about the potential for life on venus

120
00:04:10,869 --> 00:04:09,040
um

121
00:04:15,350 --> 00:04:10,879
and you know whether or not alien life

122
00:04:16,949 --> 00:04:15,360
was there

123
00:04:18,710 --> 00:04:16,959
so given the importance of this

124
00:04:19,189 --> 00:04:18,720
discovery and the obvious public

125
00:04:21,189 --> 00:04:19,199
interest

126
00:04:23,670 --> 00:04:21,199
um in this question um the scientific

127
00:04:25,590 --> 00:04:23,680
community responded to this discovery

128
00:04:27,030 --> 00:04:25,600
by seeking answer to the following five

129
00:04:28,790 --> 00:04:27,040
questions

130
00:04:31,590 --> 00:04:28,800
first of all can the detection of a

131
00:04:33,350 --> 00:04:31,600
feature at 266.94 gigahertz be

132
00:04:35,430 --> 00:04:33,360
verified by others not just by the

133
00:04:37,110 --> 00:04:35,440
discovery team

134
00:04:38,629 --> 00:04:37,120
are there other features indicative of

135
00:04:40,629 --> 00:04:38,639
phosphine elsewhere in the venus

136
00:04:43,670 --> 00:04:40,639
spectrum because the gold standard

137
00:04:46,710 --> 00:04:43,680
for the detection of a molecule

138
00:04:48,230 --> 00:04:46,720
is not just um being able to observe

139
00:04:49,590 --> 00:04:48,240
with multiple instruments in a different

140
00:04:51,189 --> 00:04:49,600
epochs which was done

141
00:04:52,950 --> 00:04:51,199
but also being able to show that

142
00:04:55,270 --> 00:04:52,960
multiple lines or bands of the same

143
00:04:56,870 --> 00:04:55,280
molecule are present in the spectrum

144
00:04:58,070 --> 00:04:56,880
or was there evidence of phosphine in

145
00:04:59,590 --> 00:04:58,080
other measurements of the venous

146
00:05:01,270 --> 00:04:59,600
atmosphere

147
00:05:03,510 --> 00:05:01,280
is the feature due to phosphine or some

148
00:05:04,870 --> 00:05:03,520
other explanation more likely

149
00:05:06,550 --> 00:05:04,880
are there ways that phosphine could be

150
00:05:07,749 --> 00:05:06,560
made abiotically in the venous

151
00:05:09,430 --> 00:05:07,759
atmosphere

152
00:05:11,189 --> 00:05:09,440
and is it likely that life exists in

153
00:05:12,950 --> 00:05:11,199
this environment and in fact produces

154
00:05:14,830 --> 00:05:12,960
phosphine

155
00:05:18,629 --> 00:05:14,840
so kind of detection of a feature at

156
00:05:20,469 --> 00:05:18,639
266.94 gigahertz be verified by others

157
00:05:22,070 --> 00:05:20,479
so the great thing about this discovery

158
00:05:23,990 --> 00:05:22,080
was that the armored data were released

159
00:05:25,670 --> 00:05:24,000
right on publication of the paper

160
00:05:28,710 --> 00:05:25,680
which allowed several other teams to

161
00:05:30,310 --> 00:05:28,720
very rapidly check the data

162
00:05:32,710 --> 00:05:30,320
so the first team that published on this

163
00:05:35,350 --> 00:05:32,720
was led by ignac snellen

164
00:05:37,029 --> 00:05:35,360
and their conclusion was that the 266.94

165
00:05:39,990 --> 00:05:37,039
gigahertz on the line was in fact

166
00:05:42,150 --> 00:05:40,000
not detected and their argument was that

167
00:05:44,550 --> 00:05:42,160
in fact a 12th order polynomial that was

168
00:05:45,909 --> 00:05:44,560
used to fit the rather ripply continuum

169
00:05:49,350 --> 00:05:45,919
of the data

170
00:05:51,749 --> 00:05:49,360
had in fact given invalid prominence to

171
00:05:53,670 --> 00:05:51,759
essentially a noise feature making it

172
00:05:56,870 --> 00:05:53,680
appear as if it was an absorption

173
00:05:58,950 --> 00:05:56,880
um an absorption line

174
00:06:00,950 --> 00:05:58,960
so using the twelfth order polynomial

175
00:06:02,309 --> 00:06:00,960
they were able to reproduce the results

176
00:06:03,830 --> 00:06:02,319
that greaves it all got but when they

177
00:06:07,110 --> 00:06:03,840
used a more modest third i'll

178
00:06:10,309 --> 00:06:07,120
order polynomial to fit the data the

179
00:06:11,749 --> 00:06:10,319
detection at the phosphine uh frequency

180
00:06:15,909 --> 00:06:11,759
not only dropped to only

181
00:06:17,670 --> 00:06:15,919
two sigma but also other lines um

182
00:06:21,350 --> 00:06:17,680
uh yeah it was not and that was not

183
00:06:22,950 --> 00:06:21,360
considered statistically significant

184
00:06:24,469 --> 00:06:22,960
in another paper following on from that

185
00:06:27,350 --> 00:06:24,479
but the inaudible

186
00:06:30,150 --> 00:06:27,360
um they claimed also that they could not

187
00:06:32,230 --> 00:06:30,160
reproduce the detection of the 266.94

188
00:06:34,070 --> 00:06:32,240
gigahertz on the line

189
00:06:37,029 --> 00:06:34,080
and again this is because the polynomial

190
00:06:39,189 --> 00:06:37,039
fit may have artificially produced

191
00:06:43,590 --> 00:06:39,199
essentially an absorption band um at

192
00:06:47,270 --> 00:06:46,550
so while this was going on um the armor

193
00:06:48,790 --> 00:06:47,280
team

194
00:06:50,469 --> 00:06:48,800
at the telescope discovered that the

195
00:06:52,469 --> 00:06:50,479
data had in fact not been

196
00:06:53,990 --> 00:06:52,479
calibrated as well as it could have been

197
00:06:57,189 --> 00:06:54,000
and so they re

198
00:07:00,230 --> 00:06:57,199
released the data with a new calibration

199
00:07:02,710 --> 00:07:00,240
so grieves it al on re-analyzing the

200
00:07:04,790 --> 00:07:02,720
updated calibration for the data um

201
00:07:06,629 --> 00:07:04,800
showed that in fact indeed the phosphine

202
00:07:08,309 --> 00:07:06,639
was not detected at the significance

203
00:07:08,790 --> 00:07:08,319
that was seen in the original discovery

204
00:07:11,270 --> 00:07:08,800
data

205
00:07:11,990 --> 00:07:11,280
with the with the incorrect calibration

206
00:07:13,990 --> 00:07:12,000
um but they

207
00:07:16,390 --> 00:07:14,000
they claimed that phosphine was still in

208
00:07:18,710 --> 00:07:16,400
fact seen at the the frequency

209
00:07:20,309 --> 00:07:18,720
um that was expected but that now

210
00:07:21,909 --> 00:07:20,319
instead of 20 parts per billion it was

211
00:07:24,070 --> 00:07:21,919
much more likely to be

212
00:07:25,589 --> 00:07:24,080
at least one part per billion of

213
00:07:27,670 --> 00:07:25,599
phosphine

214
00:07:29,510 --> 00:07:27,680
um they argue this is reconcilable with

215
00:07:31,430 --> 00:07:29,520
the 20 parts per billion of phosphine

216
00:07:33,589 --> 00:07:31,440
seen in the jcmt

217
00:07:34,710 --> 00:07:33,599
which was not subject to a recalibration

218
00:07:36,150 --> 00:07:34,720
recall

219
00:07:37,909 --> 00:07:36,160
and said that that was potentially due

220
00:07:41,350 --> 00:07:37,919
to temporal variability

221
00:07:43,909 --> 00:07:41,360
in phosphine in the venous atmosphere

222
00:07:45,990 --> 00:07:43,919
a team led by alex aikens then also

223
00:07:47,350 --> 00:07:46,000
looked again at this recalibrated data

224
00:07:48,629 --> 00:07:47,360
so not the original stuff but the

225
00:07:53,270 --> 00:07:48,639
recalibrated data

226
00:07:56,150 --> 00:07:53,280
but they were again unable to reproduce

227
00:07:56,869 --> 00:07:56,160
a an absorption line at the correct

228
00:08:00,230 --> 00:07:56,879
frequency

229
00:08:02,309 --> 00:08:00,240
even in the recalibrated data

230
00:08:03,670 --> 00:08:02,319
they went on however to explain that

231
00:08:05,749 --> 00:08:03,680
maybe that was because

232
00:08:07,589 --> 00:08:05,759
of line dilution that had occurred

233
00:08:10,390 --> 00:08:07,599
because of the observing configuration

234
00:08:11,670 --> 00:08:10,400
of the armor array so even with all of

235
00:08:13,350 --> 00:08:11,680
the baselines in the

236
00:08:14,790 --> 00:08:13,360
armor array you can get something like a

237
00:08:17,430 --> 00:08:14,800
90 dilution

238
00:08:18,309 --> 00:08:17,440
of an extended absorption which is what

239
00:08:20,390 --> 00:08:18,319
you would have

240
00:08:23,589 --> 00:08:20,400
if the gas was evenly distributed across

241
00:08:26,710 --> 00:08:23,599
the venous disc which is quite large

242
00:08:28,950 --> 00:08:26,720
but removal of the smaller than 33 meter

243
00:08:31,670 --> 00:08:28,960
baseline

244
00:08:33,829 --> 00:08:31,680
array configuration produced a very high

245
00:08:36,709 --> 00:08:33,839
dilution so 95 to 97

246
00:08:37,750 --> 00:08:36,719
dilution meaning that it was it was

247
00:08:40,310 --> 00:08:37,760
suppressing

248
00:08:42,149 --> 00:08:40,320
um the signal coming from the gas in the

249
00:08:42,949 --> 00:08:42,159
venous atmosphere by a factor of 20 to

250
00:08:45,829 --> 00:08:42,959
33

251
00:08:47,350 --> 00:08:45,839
for disc or hemispherical averages so

252
00:08:48,470 --> 00:08:47,360
the fact that nothing was detected in

253
00:08:50,389 --> 00:08:48,480
the armored data

254
00:08:53,430 --> 00:08:50,399
could have actually been a function of

255
00:08:55,829 --> 00:08:53,440
the observing array

256
00:08:56,949 --> 00:08:55,839
so um in summary the proper release of

257
00:08:58,470 --> 00:08:56,959
the discovery and subsequent

258
00:09:00,230 --> 00:08:58,480
recalibrated data sets

259
00:09:02,710 --> 00:09:00,240
allowed the community to attempt to

260
00:09:04,310 --> 00:09:02,720
replicate on this detection

261
00:09:05,990 --> 00:09:04,320
however the consensus was that no

262
00:09:07,829 --> 00:09:06,000
significant feature had been seen

263
00:09:09,590 --> 00:09:07,839
in the armor data possibly due to

264
00:09:11,350 --> 00:09:09,600
suppression by the interferometric

265
00:09:13,269 --> 00:09:11,360
technique used on an extended object

266
00:09:15,110 --> 00:09:13,279
like venus

267
00:09:16,790 --> 00:09:15,120
and as an addendum an additional paper

268
00:09:23,350 --> 00:09:16,800
by thompson also questioned the

269
00:09:24,550 --> 00:09:23,360
detection significance of the jcmt data

270
00:09:26,949 --> 00:09:24,560
so the second question that the

271
00:09:28,630 --> 00:09:26,959
community attempted to answer is that

272
00:09:30,310 --> 00:09:28,640
is is there a secondary confirmation of

273
00:09:31,190 --> 00:09:30,320
phosphine being present because if we

274
00:09:33,509 --> 00:09:31,200
can detect

275
00:09:34,949 --> 00:09:33,519
another phosphine line somewhere else in

276
00:09:36,070 --> 00:09:34,959
the in the spectrum

277
00:09:37,670 --> 00:09:36,080
that would greatly enhance our

278
00:09:39,269 --> 00:09:37,680
confidence that phosphine had in fact

279
00:09:41,590 --> 00:09:39,279
been detected

280
00:09:43,190 --> 00:09:41,600
however by re-examining ground-based

281
00:09:44,150 --> 00:09:43,200
spectra that had already been taken in

282
00:09:47,030 --> 00:09:44,160
2015

283
00:09:47,990 --> 00:09:47,040
a team led by theresa anchor as was not

284
00:09:50,389 --> 00:09:48,000
able

285
00:09:51,110 --> 00:09:50,399
to detect phosphine in this data and

286
00:09:53,509 --> 00:09:51,120
came up

287
00:09:55,269 --> 00:09:53,519
with a um an upper limit for phosphine

288
00:09:57,030 --> 00:09:55,279
of about five parts per billion which

289
00:09:59,350 --> 00:09:57,040
was four times less than that claimed

290
00:10:00,630 --> 00:09:59,360
but in the greaves at ljcmt data the 20

291
00:10:03,350 --> 00:10:00,640
part per billion

292
00:10:04,230 --> 00:10:03,360
so no phosphine detected there and it

293
00:10:06,150 --> 00:10:04,240
should be

294
00:10:07,750 --> 00:10:06,160
a factor for at least less than what

295
00:10:10,870 --> 00:10:07,760
we're seeing

296
00:10:12,710 --> 00:10:10,880
um trumpet is owl um reanalyzed

297
00:10:14,949 --> 00:10:12,720
measurements taken by the venus express

298
00:10:15,990 --> 00:10:14,959
mission which is um was in orbit around

299
00:10:18,949 --> 00:10:16,000
venus for its uh

300
00:10:21,190 --> 00:10:18,959
its main mission um and looking at

301
00:10:22,870 --> 00:10:21,200
spectra near 4.1 microns they also

302
00:10:24,230 --> 00:10:22,880
searched for phosphine signatures there

303
00:10:27,509 --> 00:10:24,240
and did not find it

304
00:10:30,389 --> 00:10:27,519
um producing an upper limit on phosphine

305
00:10:33,350 --> 00:10:30,399
of 0.2 to 0.4 parts per billion

306
00:10:33,750 --> 00:10:33,360
in the venus atmosphere and as an aside

307
00:10:46,310 --> 00:10:33,760
a

308
00:10:50,310 --> 00:10:46,320
shows up

309
00:10:51,910 --> 00:10:50,320
in terrestrial atmospheres

310
00:10:54,069 --> 00:10:51,920
so another way of going after a

311
00:10:55,110 --> 00:10:54,079
potential validation of the phosphine

312
00:10:57,190 --> 00:10:55,120
detection

313
00:10:58,710 --> 00:10:57,200
was to re-analyze data taken from the

314
00:11:01,110 --> 00:10:58,720
pioneer venus large pro

315
00:11:03,030 --> 00:11:01,120
neutral mass spectrometer on descent

316
00:11:04,550 --> 00:11:03,040
through the venous clouds

317
00:11:07,490 --> 00:11:04,560
and so in this particular case in a

318
00:11:09,030 --> 00:11:07,500
paper led by um by mogul adele

319
00:11:11,350 --> 00:11:09,040
[Music]

320
00:11:12,870 --> 00:11:11,360
essentially looked at this mass

321
00:11:13,750 --> 00:11:12,880
measurement within the spectrometer

322
00:11:16,230 --> 00:11:13,760
which could

323
00:11:17,829 --> 00:11:16,240
be phosphine or it could also be h2s

324
00:11:20,870 --> 00:11:17,839
which has the same mass

325
00:11:23,829 --> 00:11:20,880
molecularly so in the original analysis

326
00:11:26,949 --> 00:11:23,839
of these data taken in 1980

327
00:11:29,430 --> 00:11:26,959
the uh the feature was attributed

328
00:11:31,030 --> 00:11:29,440
to nothing but h2s and so that's the fit

329
00:11:33,430 --> 00:11:31,040
of the h2s to the 3d

330
00:11:35,509 --> 00:11:33,440
data points but the authors here argue

331
00:11:37,829 --> 00:11:35,519
that in fact by fitting it with 80

332
00:11:39,350 --> 00:11:37,839
phosphine and 20 hydrogen sulfide you

333
00:11:44,389 --> 00:11:39,360
can get a better fit

334
00:11:47,670 --> 00:11:45,990
however no abundance of phosphate was

335
00:11:48,870 --> 00:11:47,680
calculated and so the value cannot be

336
00:11:50,150 --> 00:11:48,880
compared to other measurements and

337
00:11:51,590 --> 00:11:50,160
detection limits to check for

338
00:11:53,190 --> 00:11:51,600
consistency to see if it's

339
00:11:55,110 --> 00:11:53,200
right in the same ballpark as that which

340
00:11:56,870 --> 00:11:55,120
was observed elsewhere

341
00:11:59,030 --> 00:11:56,880
however when originally attributed to

342
00:12:00,870 --> 00:11:59,040
h2s the abundance was estimated to be

343
00:12:02,710 --> 00:12:00,880
three plus or minus two parts per

344
00:12:04,389 --> 00:12:02,720
million so a thousand times more than a

345
00:12:08,629 --> 00:12:04,399
part per billion

346
00:12:11,350 --> 00:12:10,230
so in summary several groups attempted

347
00:12:12,790 --> 00:12:11,360
to increase our confidence in the

348
00:12:14,629 --> 00:12:12,800
phosphate detection by searching for

349
00:12:16,069 --> 00:12:14,639
additional signs of phosphine um in

350
00:12:17,829 --> 00:12:16,079
other data sets

351
00:12:19,350 --> 00:12:17,839
but spectroscopic observations there 4

352
00:12:20,949 --> 00:12:19,360
and 10 microns failed to detect the

353
00:12:23,990 --> 00:12:20,959
phosphine and set an upper limit that

354
00:12:26,629 --> 00:12:24,000
was between 5 to 0.2 parts per billion

355
00:12:28,629 --> 00:12:26,639
and then re-analysis that pioneer venus

356
00:12:30,389 --> 00:12:28,639
neutral mass spectrometer data

357
00:12:32,310 --> 00:12:30,399
was interpreted to include phosphate in

358
00:12:33,509 --> 00:12:32,320
the measurements previously attributed

359
00:12:36,829 --> 00:12:33,519
to h2s

360
00:12:42,790 --> 00:12:36,839
but the corresponding abundance was not

361
00:12:46,230 --> 00:12:44,550
so the next question we can ask is is

362
00:12:47,750 --> 00:12:46,240
the feature due to phosphine or some

363
00:12:48,710 --> 00:12:47,760
other molecule more likely so if the

364
00:12:51,509 --> 00:12:48,720
phosphine actually

365
00:12:53,190 --> 00:12:51,519
is there and after the previous analyses

366
00:12:54,310 --> 00:12:53,200
it's not entirely clear that it is but

367
00:12:56,069 --> 00:12:54,320
if it is there

368
00:12:57,910 --> 00:12:56,079
um is it due to phosphine or could it be

369
00:12:59,990 --> 00:12:57,920
due to something else

370
00:13:02,230 --> 00:13:00,000
so v in a way that al suggested that in

371
00:13:02,949 --> 00:13:02,240
fact time variable so2 could explain the

372
00:13:05,110 --> 00:13:02,959
data

373
00:13:05,990 --> 00:13:05,120
um and they fit and evenly mixed 100

374
00:13:09,350 --> 00:13:06,000
parts per billion

375
00:13:12,629 --> 00:13:09,360
of so2 in the mesosphere um

376
00:13:15,750 --> 00:13:12,639
and 10 parts per billion uh in the uh

377
00:13:17,990 --> 00:13:15,760
jcmt data sorry in the armor data and

378
00:13:20,470 --> 00:13:18,000
100 in the jcmt data and so that that

379
00:13:22,069 --> 00:13:20,480
could in fact um fit the data

380
00:13:23,990 --> 00:13:22,079
so they invoke temporal variability in

381
00:13:24,710 --> 00:13:24,000
so2 for the different scene and two data

382
00:13:26,550 --> 00:13:24,720
sets

383
00:13:28,230 --> 00:13:26,560
and they use line with arguments to rule

384
00:13:30,069 --> 00:13:28,240
out the line core being formed within

385
00:13:31,670 --> 00:13:30,079
the clouds so the line core is the the

386
00:13:34,550 --> 00:13:31,680
center of the absorption

387
00:13:36,150 --> 00:13:34,560
of the line out here we have the wings

388
00:13:37,750 --> 00:13:36,160
closer to the continuum

389
00:13:39,670 --> 00:13:37,760
but the line core was what was most

390
00:13:41,350 --> 00:13:39,680
prominently seen and the point was that

391
00:13:43,269 --> 00:13:41,360
that line core was sufficiently

392
00:13:45,670 --> 00:13:43,279
narrow and sufficiently prominent in the

393
00:13:48,310 --> 00:13:45,680
core that it was coming potentially from

394
00:13:50,310 --> 00:13:48,320
the upper atmosphere

395
00:13:52,230 --> 00:13:50,320
grieves that island response um and this

396
00:13:53,269 --> 00:13:52,240
was an ongoing discussion that ended up

397
00:13:56,470 --> 00:13:53,279
in the archive

398
00:13:56,949 --> 00:13:56,480
um from nature matters arising um argued

399
00:13:59,509 --> 00:13:56,959
that

400
00:14:01,829 --> 00:13:59,519
the 266.94 gigahertz line could not be

401
00:14:03,910 --> 00:14:01,839
attributed to so2 because the line width

402
00:14:05,189 --> 00:14:03,920
um in their observed detection which is

403
00:14:07,590 --> 00:14:05,199
this thing here

404
00:14:10,310 --> 00:14:07,600
um was larger than that observed for so2

405
00:14:11,990 --> 00:14:10,320
features seen at other wavelengths

406
00:14:13,670 --> 00:14:12,000
and that the required abundance and they

407
00:14:15,110 --> 00:14:13,680
felt they needed to fit it with 150

408
00:14:17,030 --> 00:14:15,120
parts per billion of so2

409
00:14:18,150 --> 00:14:17,040
would be an extreme outlier compared

410
00:14:20,389 --> 00:14:18,160
with other values

411
00:14:23,430 --> 00:14:20,399
of so2 that had been seen in the venus

412
00:14:26,550 --> 00:14:25,350
so in another paper led by andrew

413
00:14:30,069 --> 00:14:26,560
linkowski and

414
00:14:32,710 --> 00:14:30,079
al they used a radiator transfer

415
00:14:33,509 --> 00:14:32,720
model to actually look at where the

416
00:14:35,750 --> 00:14:33,519
absorption

417
00:14:37,189 --> 00:14:35,760
was coming from in the venous atmosphere

418
00:14:39,910 --> 00:14:37,199
and they showed using radius

419
00:14:40,949 --> 00:14:39,920
jacobians um that at least in the case

420
00:14:43,509 --> 00:14:40,959
of phosphine

421
00:14:44,470 --> 00:14:43,519
in that lying position um the phosphine

422
00:14:46,470 --> 00:14:44,480
was coming from

423
00:14:48,150 --> 00:14:46,480
above 75 kilometers in the venus

424
00:14:49,189 --> 00:14:48,160
atmosphere so not within the clouds

425
00:14:50,230 --> 00:14:49,199
where it would be protected from

426
00:14:52,150 --> 00:14:50,240
destruction

427
00:14:54,470 --> 00:14:52,160
but up very high in the atmosphere where

428
00:14:56,389 --> 00:14:54,480
it was vulnerable to being destroyed

429
00:14:58,389 --> 00:14:56,399
and in fact to maintain 20 parts per

430
00:15:00,230 --> 00:14:58,399
billion at these altitudes the flux of

431
00:15:02,230 --> 00:15:00,240
phosphine would have to exceed a hundred

432
00:15:03,030 --> 00:15:02,240
times the earth's photosynthetic oxygen

433
00:15:06,550 --> 00:15:03,040
flux

434
00:15:08,310 --> 00:15:06,560
maintain phosphine at these sorts of

435
00:15:11,910 --> 00:15:08,320
altitudes

436
00:15:13,189 --> 00:15:11,920
when cascadel also modeled the jcmt data

437
00:15:15,829 --> 00:15:13,199
but they did it using

438
00:15:17,670 --> 00:15:15,839
a realistic profile for sulfur dioxide

439
00:15:18,310 --> 00:15:17,680
down through the venus atmosphere which

440
00:15:20,069 --> 00:15:18,320
matched

441
00:15:22,389 --> 00:15:20,079
previous spacecraft data so this was a

442
00:15:24,629 --> 00:15:22,399
realistic so2 profile

443
00:15:26,389 --> 00:15:24,639
matched to spacecraft data i mean they

444
00:15:29,350 --> 00:15:26,399
were able to very well fit

445
00:15:30,069 --> 00:15:29,360
on the jcmt data both the widths and the

446
00:15:34,069 --> 00:15:30,079
depth

447
00:15:35,670 --> 00:15:34,079
of the feature using so2 alone

448
00:15:37,590 --> 00:15:35,680
however this fit would have predicted

449
00:15:39,350 --> 00:15:37,600
that that so2 reference line that was

450
00:15:42,550 --> 00:15:39,360
used for contamination

451
00:15:44,389 --> 00:15:42,560
removal would in fact have been

452
00:15:53,189 --> 00:15:44,399
you know 10 times larger than the limit

453
00:15:59,509 --> 00:15:56,470
however um because

454
00:16:01,990 --> 00:15:59,519
of the the possibility of line dilution

455
00:16:02,949 --> 00:16:02,000
and that um the the shorter bass lines

456
00:16:05,189 --> 00:16:02,959
being removed

457
00:16:07,350 --> 00:16:05,199
it's quite possible that any so2 that

458
00:16:09,110 --> 00:16:07,360
was seen at that reference wavelength

459
00:16:10,790 --> 00:16:09,120
was in fact heavily suppressed

460
00:16:12,710 --> 00:16:10,800
and so the fact that it was not seen was

461
00:16:13,749 --> 00:16:12,720
perhaps not a surprise

462
00:16:17,030 --> 00:16:13,759
but it didn't mean that the

463
00:16:19,430 --> 00:16:17,040
contamination test uh was compromised

464
00:16:20,790 --> 00:16:19,440
uh because if you couldn't see the so2

465
00:16:22,629 --> 00:16:20,800
then you couldn't tell how much of it

466
00:16:26,230 --> 00:16:22,639
was there to be able to subtract it off

467
00:16:30,629 --> 00:16:28,870
but it also means that as seen in the in

468
00:16:31,990 --> 00:16:30,639
the linkowski paper that if you fit the

469
00:16:33,829 --> 00:16:32,000
jcmt line

470
00:16:35,189 --> 00:16:33,839
you therefore due to line suppression

471
00:16:38,230 --> 00:16:35,199
don't expect to see an

472
00:16:40,629 --> 00:16:38,240
so2 feature at that particular position

473
00:16:42,389 --> 00:16:40,639
and so the so2 hypothesis could explain

474
00:16:44,310 --> 00:16:42,399
both the jcmt feature

475
00:16:45,749 --> 00:16:44,320
and the lack of a feature in the armor

476
00:16:47,749 --> 00:16:45,759
data

477
00:16:49,829 --> 00:16:47,759
so in summary plausible venus upper

478
00:16:51,590 --> 00:16:49,839
atmospheric so2 was shown to produce a

479
00:16:53,350 --> 00:16:51,600
signal that fit the width and depth of

480
00:16:54,870 --> 00:16:53,360
the jcmt data

481
00:16:57,990 --> 00:16:54,880
line dilution from the armor array

482
00:16:59,990 --> 00:16:58,000
configuration predicted that little

483
00:17:01,910 --> 00:17:00,000
or no signal could be seen in the armor

484
00:17:03,350 --> 00:17:01,920
data as was the case after the

485
00:17:05,909 --> 00:17:03,360
recalibration

486
00:17:08,069 --> 00:17:05,919
in fact of that data and for phosphine

487
00:17:09,750 --> 00:17:08,079
to fit the jcmt data it would have to be

488
00:17:11,429 --> 00:17:09,760
present above the clouds

489
00:17:12,870 --> 00:17:11,439
where the high flux needed to maintain

490
00:17:16,309 --> 00:17:12,880
it against destruction would be

491
00:17:19,429 --> 00:17:17,669
so the next question the community

492
00:17:20,949 --> 00:17:19,439
looked at was can phosphate be formed

493
00:17:23,669 --> 00:17:20,959
abiotically in the venous

494
00:17:25,510 --> 00:17:23,679
environment so in both the discovery

495
00:17:27,750 --> 00:17:25,520
paper and in an extensive companion

496
00:17:30,710 --> 00:17:27,760
paper i'm led by william baines

497
00:17:32,710 --> 00:17:30,720
um the authors argue that phosphine

498
00:17:34,230 --> 00:17:32,720
cannot be produced by any known surface

499
00:17:36,950 --> 00:17:34,240
interior atmosphere lightning or

500
00:17:39,430 --> 00:17:36,960
meteoritic process

501
00:17:40,230 --> 00:17:39,440
and so that made perhaps the life

502
00:17:42,070 --> 00:17:40,240
hypothesis

503
00:17:44,390 --> 00:17:42,080
potentially more likely or some other

504
00:17:46,470 --> 00:17:44,400
process that we're not thinking about

505
00:17:48,070 --> 00:17:46,480
jerome and lunine argued instead that

506
00:17:49,510 --> 00:17:48,080
trace amounts of phosphites could be

507
00:17:51,270 --> 00:17:49,520
formed in the mantle and volcanically

508
00:17:53,909 --> 00:17:51,280
ejected and react with water or sulfuric

509
00:17:55,990 --> 00:17:53,919
acid to form phosphine

510
00:17:57,669 --> 00:17:56,000
mikhail zolotov counter argued that the

511
00:17:59,350 --> 00:17:57,679
measured amount of phosphine was in fact

512
00:18:00,549 --> 00:17:59,360
inconsistent with the known phosphorus

513
00:18:02,230 --> 00:18:00,559
budget for venus

514
00:18:04,310 --> 00:18:02,240
as phosphorus was unlikely to come from

515
00:18:06,150 --> 00:18:04,320
the interior as is the case on earth we

516
00:18:07,190 --> 00:18:06,160
get little unknown phosphine coming from

517
00:18:08,470 --> 00:18:07,200
our interior

518
00:18:09,990 --> 00:18:08,480
and the amount of frosting needed to

519
00:18:12,830 --> 00:18:10,000
explain the data was in fact well in

520
00:18:15,270 --> 00:18:12,840
excess of that expected from meteoritic

521
00:18:16,950 --> 00:18:15,280
sources

522
00:18:18,630 --> 00:18:16,960
another question then is is it likely

523
00:18:21,669 --> 00:18:18,640
that life exists in the environment

524
00:18:23,830 --> 00:18:21,679
and produces phosphine

525
00:18:25,350 --> 00:18:23,840
and so the survival and biological

526
00:18:27,029 --> 00:18:25,360
generation of phosphine has looked

527
00:18:29,110 --> 00:18:27,039
been looked at by a number of authors

528
00:18:31,830 --> 00:18:29,120
over the years the most recent was the

529
00:18:34,070 --> 00:18:31,840
the review by sigrid allen 2020

530
00:18:35,750 --> 00:18:34,080
um which dylan it delineated the

531
00:18:37,909 --> 00:18:35,760
multiple compound difficulties that life

532
00:18:40,630 --> 00:18:37,919
will face in the venus atmosphere

533
00:18:42,310 --> 00:18:40,640
and a very recent paper by holsworthy

534
00:18:44,150 --> 00:18:42,320
which i think the venus clouds likely

535
00:18:46,470 --> 00:18:44,160
have water activities two orders of

536
00:18:47,990 --> 00:18:46,480
magnitude below the level survivable by

537
00:18:50,230 --> 00:18:48,000
earth extremophiles

538
00:18:51,750 --> 00:18:50,240
and so essentially what that means um is

539
00:18:52,630 --> 00:18:51,760
that water is not available for

540
00:18:56,310 --> 00:18:52,640
biological

541
00:18:58,630 --> 00:18:56,320
um reactions within the venus clouds

542
00:18:59,990 --> 00:18:58,640
and the other argument against life

543
00:19:01,830 --> 00:19:00,000
producing the phosphine

544
00:19:03,510 --> 00:19:01,840
is that the because the observed lining

545
00:19:05,750 --> 00:19:03,520
profile for the jcmt showed the

546
00:19:07,350 --> 00:19:05,760
phosphine was high above the cloud tops

547
00:19:09,110 --> 00:19:07,360
then the flux needed to maintain it up

548
00:19:10,470 --> 00:19:09,120
there is biologically improbable because

549
00:19:13,990 --> 00:19:10,480
it would have to exceed

550
00:19:14,549 --> 00:19:14,000
um the uh by many times the oxygenic

551
00:19:19,909 --> 00:19:14,559
flux

552
00:19:21,990 --> 00:19:19,919
from oxygenic photosynthesis on our own

553
00:19:23,110 --> 00:19:22,000
planet so it's perhaps unlikely that a

554
00:19:25,029 --> 00:19:23,120
biosphere

555
00:19:27,510 --> 00:19:25,039
in venous conditions could be that

556
00:19:29,270 --> 00:19:27,520
projective overall

557
00:19:30,950 --> 00:19:29,280
moreover if the absorption really is

558
00:19:32,789 --> 00:19:30,960
coming from high up

559
00:19:34,070 --> 00:19:32,799
then for phosphine you would expect the

560
00:19:36,230 --> 00:19:34,080
vertical distribution

561
00:19:38,150 --> 00:19:36,240
in of the gas in the atmosphere to drop

562
00:19:38,950 --> 00:19:38,160
off extremely rapidly above the clouds

563
00:19:42,070 --> 00:19:38,960
because of the rate

564
00:19:44,150 --> 00:19:42,080
which is destroyed up there but as a

565
00:19:46,230 --> 00:19:44,160
counter perhaps so2 is more likely

566
00:19:47,669 --> 00:19:46,240
because we know that so2 does exist each

567
00:19:48,549 --> 00:19:47,679
dot here is a measurement taken by a

568
00:19:50,549 --> 00:19:48,559
spacecraft

569
00:19:52,470 --> 00:19:50,559
so so2 is known to exist in the

570
00:19:54,390 --> 00:19:52,480
atmosphere above the venous clouds and

571
00:19:55,350 --> 00:19:54,400
in fact to increase with altitude so it

572
00:19:57,110 --> 00:19:55,360
does not

573
00:20:00,150 --> 00:19:57,120
have a problem with being up at these

574
00:20:02,789 --> 00:20:00,160
types of altitudes

575
00:20:04,470 --> 00:20:02,799
so let's then consider looking at what

576
00:20:06,630 --> 00:20:04,480
we've learned about venus and about

577
00:20:08,390 --> 00:20:06,640
trying to verify the venus observations

578
00:20:11,270 --> 00:20:08,400
and think of a possible framework for

579
00:20:12,549 --> 00:20:11,280
standards of evidence for biosignatures

580
00:20:14,789 --> 00:20:12,559
so the first question we have to ask

581
00:20:16,870 --> 00:20:14,799
ourselves is have you detected something

582
00:20:18,390 --> 00:20:16,880
um or are you in fact observing some

583
00:20:19,909 --> 00:20:18,400
kind of instrumental artifact or

584
00:20:21,190 --> 00:20:19,919
something that is has come out in the

585
00:20:23,029 --> 00:20:21,200
processing

586
00:20:24,870 --> 00:20:23,039
have you correctly identified what you

587
00:20:25,510 --> 00:20:24,880
think you've detected can you verify

588
00:20:27,669 --> 00:20:25,520
that this

589
00:20:29,270 --> 00:20:27,679
is in fact indeed um you know the

590
00:20:30,630 --> 00:20:29,280
molecule that you think you have or is

591
00:20:32,310 --> 00:20:30,640
there some sort of contamination that

592
00:20:34,070 --> 00:20:32,320
you haven't ruled out

593
00:20:35,590 --> 00:20:34,080
other abiotic sources for what you think

594
00:20:37,029 --> 00:20:35,600
you've detected but it makes sense for

595
00:20:38,630 --> 00:20:37,039
life to produce this compound or

596
00:20:40,390 --> 00:20:38,640
expression in this environment

597
00:20:41,750 --> 00:20:40,400
and finally other independent lines of

598
00:20:43,590 --> 00:20:41,760
evidence supporting a biological

599
00:20:45,990 --> 00:20:43,600
explanation

600
00:20:46,789 --> 00:20:46,000
so in all of these steps we need some

601
00:20:48,630 --> 00:20:46,799
assessment of

602
00:20:50,310 --> 00:20:48,640
our standards of confidence of each step

603
00:20:52,310 --> 00:20:50,320
which we can hopefully feed into some

604
00:20:54,470 --> 00:20:52,320
sort of statistical assessment

605
00:20:57,430 --> 00:20:54,480
of the probability of life on non-life

606
00:20:59,270 --> 00:20:57,440
producing the observed phenomena

607
00:21:01,190 --> 00:20:59,280
so we think if we think in the framework

608
00:21:03,909 --> 00:21:01,200
of this sort of um

609
00:21:05,350 --> 00:21:03,919
uh sort of standards of evidence and and

610
00:21:07,190 --> 00:21:05,360
confidence scale

611
00:21:08,789 --> 00:21:07,200
then if we look at the initial discovery

612
00:21:10,630 --> 00:21:08,799
um of the claimed evidence of phosphate

613
00:21:12,470 --> 00:21:10,640
in the venous clouds

614
00:21:13,990 --> 00:21:12,480
then it looks quite robust there are

615
00:21:17,990 --> 00:21:14,000
three detections of a high signal

616
00:21:19,270 --> 00:21:18,000
noise feature um at 266.94 gigahertz

617
00:21:20,710 --> 00:21:19,280
and the observations were taken with

618
00:21:21,830 --> 00:21:20,720
multiple telescopes instruments and

619
00:21:23,110 --> 00:21:21,840
epochs

620
00:21:24,950 --> 00:21:23,120
there was apparently little or no

621
00:21:27,590 --> 00:21:24,960
contamination for so2 and a

622
00:21:29,430 --> 00:21:27,600
contamination test had been set up

623
00:21:30,630 --> 00:21:29,440
and was able to rule out so2

624
00:21:32,390 --> 00:21:30,640
contamination

625
00:21:34,310 --> 00:21:32,400
so at that point this discovery was at a

626
00:21:36,310 --> 00:21:34,320
preliminary confidence level i think of

627
00:21:37,270 --> 00:21:36,320
about two on our biosignature assessment

628
00:21:38,789 --> 00:21:37,280
framework

629
00:21:40,710 --> 00:21:38,799
it appeared that there was a robust

630
00:21:42,310 --> 00:21:40,720
detection and that it was indeed due to

631
00:21:43,590 --> 00:21:42,320
phosphine because the so2 had been

632
00:21:45,430 --> 00:21:43,600
rolled out

633
00:21:47,029 --> 00:21:45,440
however recalibration of the armor

634
00:21:48,870 --> 00:21:47,039
discovery data and then subsequent work

635
00:21:49,669 --> 00:21:48,880
by the community to attempt to validate

636
00:21:51,510 --> 00:21:49,679
the detection

637
00:21:53,510 --> 00:21:51,520
served to sort of reduce that overall

638
00:21:55,029 --> 00:21:53,520
significance of the detection

639
00:21:56,870 --> 00:21:55,039
so recalibration showed that the

640
00:21:57,990 --> 00:21:56,880
original 15 sigma armor line was an

641
00:21:59,669 --> 00:21:58,000
artifact

642
00:22:01,510 --> 00:21:59,679
several independent groups could not

643
00:22:03,270 --> 00:22:01,520
reproduce the detected line

644
00:22:04,549 --> 00:22:03,280
in the discovery or the recalibrated

645
00:22:06,070 --> 00:22:04,559
data

646
00:22:07,430 --> 00:22:06,080
and attempts to find corroborating

647
00:22:08,789 --> 00:22:07,440
evidence for phosphine and other

648
00:22:11,990 --> 00:22:08,799
spectral wavelengths

649
00:22:13,590 --> 00:22:12,000
fail to detect the phosphine

650
00:22:15,590 --> 00:22:13,600
community members also called in the

651
00:22:19,190 --> 00:22:15,600
question that so2 contamination

652
00:22:21,029 --> 00:22:19,200
test um and explained that ss2 may not

653
00:22:23,750 --> 00:22:21,039
have been seen in the armada due to line

654
00:22:25,110 --> 00:22:23,760
suppression not a lack of so2

655
00:22:28,310 --> 00:22:25,120
and since light suppression would not

656
00:22:31,190 --> 00:22:28,320
have affected the single dish jcmt data

657
00:22:32,549 --> 00:22:31,200
um then you can't assume that there's no

658
00:22:34,310 --> 00:22:32,559
so2 there and if

659
00:22:35,590 --> 00:22:34,320
therefore all of the line is seen by

660
00:22:37,510 --> 00:22:35,600
biphosphine

661
00:22:38,630 --> 00:22:37,520
and in fact radiative transfer models

662
00:22:41,190 --> 00:22:38,640
showed that in fact

663
00:22:43,669 --> 00:22:41,200
typical venus so2 could fit the gcmt

664
00:22:46,310 --> 00:22:43,679
data without the need for phosphine

665
00:22:47,669 --> 00:22:46,320
and if the line core is indeed coming

666
00:22:50,230 --> 00:22:47,679
from above the clouds as several

667
00:22:52,230 --> 00:22:50,240
researchers pointed out

668
00:22:54,149 --> 00:22:52,240
then it's statistically more likely that

669
00:22:55,990 --> 00:22:54,159
that's going to be so2 which we know

670
00:22:57,669 --> 00:22:56,000
persists and increases with altitude

671
00:22:59,430 --> 00:22:57,679
rather than phosphine which has an

672
00:23:02,310 --> 00:22:59,440
incredibly short lifetime come

673
00:23:03,270 --> 00:23:02,320
above the clouds so while additional

674
00:23:04,950 --> 00:23:03,280
work can be done

675
00:23:06,870 --> 00:23:04,960
in understanding possible abiotic

676
00:23:08,390 --> 00:23:06,880
sources for phosphine and the venous

677
00:23:10,630 --> 00:23:08,400
atmosphere and the likelihood that life

678
00:23:12,230 --> 00:23:10,640
can persist and produce phosphine there

679
00:23:14,070 --> 00:23:12,240
i think the highest priority for future

680
00:23:15,830 --> 00:23:14,080
work on this particular issue

681
00:23:17,669 --> 00:23:15,840
is in potentially showing up confidence

682
00:23:20,710 --> 00:23:17,679
levels one and two the detection

683
00:23:22,710 --> 00:23:20,720
and identification so we essentially

684
00:23:26,470 --> 00:23:22,720
have two hypotheses now for what

685
00:23:27,430 --> 00:23:26,480
that absorption is um in the jcmt data

686
00:23:29,270 --> 00:23:27,440
in particular

687
00:23:31,029 --> 00:23:29,280
so we need to distinguish between

688
00:23:33,909 --> 00:23:31,039
interpreting that line as phosphine

689
00:23:35,270 --> 00:23:33,919
or interpreting it as so2 only and so to

690
00:23:36,950 --> 00:23:35,280
do that there are a bunch of different

691
00:23:38,149 --> 00:23:36,960
observations that could be proposed and

692
00:23:41,350 --> 00:23:38,159
these were proposed

693
00:23:41,990 --> 00:23:41,360
largely by alex aikens first of all

694
00:23:43,510 --> 00:23:42,000
single

695
00:23:45,029 --> 00:23:43,520
dish measurements would be much better

696
00:23:48,390 --> 00:23:45,039
than using an array because they do not

697
00:23:50,390 --> 00:23:48,400
suffer from the line dilution

698
00:23:52,310 --> 00:23:50,400
or another way of getting that is using

699
00:23:53,750 --> 00:23:52,320
the atacama compact array with the much

700
00:23:56,470 --> 00:23:53,760
shorter baselines that are much more

701
00:23:58,789 --> 00:23:56,480
sensitive to broadly distributed gases

702
00:24:00,390 --> 00:23:58,799
and then for the the contamination test

703
00:24:02,070 --> 00:24:00,400
which was done really at two different

704
00:24:03,909 --> 00:24:02,080
epochs with two different instruments it

705
00:24:04,549 --> 00:24:03,919
would be better to do that at the same

706
00:24:06,630 --> 00:24:04,559
time

707
00:24:08,710 --> 00:24:06,640
with the same instrument um and so

708
00:24:10,870 --> 00:24:08,720
simultaneous observations of the so2

709
00:24:13,909 --> 00:24:10,880
reference line along with the blended

710
00:24:15,269 --> 00:24:13,919
to 266.94 gigahertz line

711
00:24:16,950 --> 00:24:15,279
would be a much more definitive

712
00:24:18,470 --> 00:24:16,960
contamination test

713
00:24:20,070 --> 00:24:18,480
and these observations should occur when

714
00:24:22,070 --> 00:24:20,080
venus has a smaller angular

715
00:24:23,669 --> 00:24:22,080
apparent angular diameter and is less

716
00:24:26,549 --> 00:24:23,679
resolved by the armor antennas which

717
00:24:30,230 --> 00:24:27,990
so one of the bigger picture takeaways

718
00:24:31,430 --> 00:24:30,240
from all of this well i think this was

719
00:24:33,909 --> 00:24:31,440
really an interesting test run for

720
00:24:35,430 --> 00:24:33,919
future exoplanet biosignature assessment

721
00:24:36,950 --> 00:24:35,440
um and what it showed us is that

722
00:24:39,110 --> 00:24:36,960
understanding the environment

723
00:24:40,950 --> 00:24:39,120
that you're trying to you know determine

724
00:24:43,110 --> 00:24:40,960
the context of this biosecurity in is

725
00:24:44,549 --> 00:24:43,120
absolutely key to searching for life

726
00:24:46,230 --> 00:24:44,559
and it's important to characterize that

727
00:24:47,909 --> 00:24:46,240
environment and if at all possible have

728
00:24:49,350 --> 00:24:47,919
colleagues who can understand what their

729
00:24:50,549 --> 00:24:49,360
environment's like and understand those

730
00:24:52,470 --> 00:24:50,559
data

731
00:24:54,470 --> 00:24:52,480
obviously for an exoplanet observation

732
00:24:56,549 --> 00:24:54,480
it's going to be extremely challenging

733
00:24:57,750 --> 00:24:56,559
um to be able to uh you know have

734
00:24:59,750 --> 00:24:57,760
someone who's an expert on that

735
00:25:01,190 --> 00:24:59,760
particular planet

736
00:25:02,789 --> 00:25:01,200
because we'll really be learning things

737
00:25:04,390 --> 00:25:02,799
in real time but nonetheless it's

738
00:25:05,590 --> 00:25:04,400
definitely worthwhile taking the time to

739
00:25:06,950 --> 00:25:05,600
look at the environment and try to

740
00:25:09,269 --> 00:25:06,960
understand what else could be there that

741
00:25:10,470 --> 00:25:09,279
could be producing your signal

742
00:25:12,149 --> 00:25:10,480
so increasing confidence and

743
00:25:13,350 --> 00:25:12,159
biosignature discovery requires at least

744
00:25:16,070 --> 00:25:13,360
four critical checks

745
00:25:18,070 --> 00:25:16,080
on detection identification the

746
00:25:19,669 --> 00:25:18,080
assessment of likely abiotic formation

747
00:25:21,350 --> 00:25:19,679
and the assessment of the plausibility

748
00:25:22,789 --> 00:25:21,360
that life can generate that product in

749
00:25:24,230 --> 00:25:22,799
its environment

750
00:25:26,390 --> 00:25:24,240
and as we're rolling out abiotic

751
00:25:28,390 --> 00:25:26,400
hypotheses i think it's also good to

752
00:25:29,669 --> 00:25:28,400
remember i think this is a great quote

753
00:25:31,190 --> 00:25:29,679
from charlie cacao

754
00:25:33,350 --> 00:25:31,200
and a very recent paper on that on the

755
00:25:37,110 --> 00:25:33,360
biosignatures that the venus

756
00:25:38,870 --> 00:25:37,120
phosphine discovery is that the biology

757
00:25:40,870 --> 00:25:38,880
hypothesis must be given the same

758
00:25:42,070 --> 00:25:40,880
rigorous examination as other possible

759
00:25:43,990 --> 00:25:42,080
hypotheses

760
00:25:46,470 --> 00:25:44,000
um it should not simply be proposed as a

761
00:25:47,750 --> 00:25:46,480
hypothesis of exclusion

762
00:25:49,029 --> 00:25:47,760
and another question we can ask

763
00:25:51,190 --> 00:25:49,039
ourselves is you know is a more

764
00:25:53,029 --> 00:25:51,200
collaborative community-wide process

765
00:25:54,470 --> 00:25:53,039
i know and you saw the the community

766
00:25:56,149 --> 00:25:54,480
come together in all of this

767
00:25:57,510 --> 00:25:56,159
likely to produce a better outcome for

768
00:25:59,269 --> 00:25:57,520
life detection

769
00:26:00,950 --> 00:25:59,279
and if so what are the best ways to

770
00:26:01,669 --> 00:26:00,960
incentivize that process and so that's

771
00:26:05,669 --> 00:26:01,679
something that we

772
00:26:06,870 --> 00:26:05,679
need to think about so um so that is the

773
00:26:09,510 --> 00:26:06,880
sort of the story of

774
00:26:11,430 --> 00:26:09,520
of phosphine and venus and again how it

775
00:26:13,430 --> 00:26:11,440
sort of leads us to this idea

776
00:26:15,590 --> 00:26:13,440
of sort of levels of confidence and how

777
00:26:17,669 --> 00:26:15,600
we might help shore up

778
00:26:18,630 --> 00:26:17,679
or find alternative explanations for a

779
00:26:21,750 --> 00:26:18,640
potential biasing

780
00:26:24,390 --> 00:26:21,760
detection and also how it behooves us to

781
00:26:27,350 --> 00:26:24,400
think about how we might want to do

782
00:26:29,029 --> 00:26:27,360
um you know life detection uh both

783
00:26:32,310 --> 00:26:29,039
confirmation and reporting

784
00:26:33,750 --> 00:26:32,320
uh overall so um i hope you'll join us

785
00:26:34,870 --> 00:26:33,760
all for the workshop that's coming up in

786
00:26:36,630 --> 00:26:34,880
a couple of weeks

787
00:26:38,070 --> 00:26:36,640
um where we'll get a chance to discuss

788
00:26:39,590 --> 00:26:38,080
both of those issues and