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Speaker 1: Now here's a highlight from Coast to coast am on iHeartRadio. Stephen.

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Speaker 2: I know, I recall from reading my UFO history that

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Speaker 2: back in the fifties had these writers who told the

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Speaker 2: public that they'd met people from Venus. They said they

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Speaker 2: even took quick trips to Venus aboard spaceships, and those Venusians,

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Speaker 2: I would think, would have to have pretty thick skin

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Speaker 2: to survive the conditions there. I mean, is it the

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Speaker 2: hottest planet as I've seen it described, hotter than Mercury,

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Speaker 2: which as far as I know, is much closer to

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Speaker 2: the Sun.

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Speaker 3: Yes, indeed, it is hotter than mercury, which seems extraordinary

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Speaker 3: given as you said that Mercury is closer to the Sun.

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Speaker 3: But of course it's all to do with its atmosphere.

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Speaker 3: Venus has an extraordinary atmosphere. It's extraordinarily complicated, and that

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Speaker 3: is a big part of the puzzle about understanding that.

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Speaker 3: So not just so that we can understand planets around

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Speaker 3: other stars, but understand what this could mean for Earth,

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Speaker 3: for example, about the future of Earth. But as you

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Speaker 3: indicated earlier, it's possible that Venus was not always like

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Speaker 3: it currently is. One of the things I always emphasize

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Speaker 3: when I'm speaking to people about this, is that it's

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Speaker 3: very important to remember that when we look at the

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Speaker 3: Solar System, whether we're looking at Jupiter or Venus or

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Speaker 3: even Earth, we're looking at these objects at an age

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Speaker 3: of four and a half billion years. That is a

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Speaker 3: lot of history behind them that we try and learn

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Speaker 3: about as best we can, and a lot of effort

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Speaker 3: goes on for the Earth in that respect, of course,

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Speaker 3: but with Venus it's a similar kind of thing. Venus

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Speaker 3: has had a whole story to evolve there, and what

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Speaker 3: we try and do is uncover that story because it

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Speaker 3: may have had a past history that looked not too

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Speaker 3: dissimilar from the Earth. And in fact, when we looked

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Speaker 3: at the Solar system when the Solar System was only

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Speaker 3: two billion years old as an alien civilization, imagine that

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Speaker 3: we're looking at our solar system two billion years ago.

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Speaker 3: Then we may have concluded that there were two Earth

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Speaker 3: sized planets, both of them with oceans. And that's quite

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Speaker 3: profound because it means that that there could have been

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Speaker 3: a much better chance for life in our Solar system

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Speaker 3: back then. But it also tells us that planets can

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Speaker 3: change in very dramatic ways during their history, and so

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Speaker 3: the big challenge for us is how does that happen,

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Speaker 3: Why does that happen? And when does that happen?

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Speaker 2: Yeah, was Venus a long ago more like Earth today?

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Speaker 2: Or was Earth now or long ago more like Venus today?

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Speaker 2: Or have both of them changed? I guess there's probably

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Speaker 2: the more likely answer.

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Speaker 3: Well, I guess this goes back to the nomenclature that

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Speaker 3: you mentioned that we often refer to Venus as being

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Speaker 3: a twin and if we follow that reasoning a little further,

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Speaker 3: what this implies is that they certainly formed at the

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Speaker 3: same time four and a half billion years ago. They

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Speaker 3: probably formed under very similar conditions and out of very

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Speaker 3: similar kinds of material, and so there probably are a

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Speaker 3: lot of similarities between them if we were to look

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Speaker 3: them at the Earth and Venus when they were both

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Speaker 3: extremely young, and so they probably started on very similar

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Speaker 3: tracks in the way in which their atmospheres were forming,

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Speaker 3: the way in which the planets were initially cooling these

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Speaker 3: surfaces we have been in a magma state as they

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Speaker 3: were cooling off from formation. The question is what happened then,

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Speaker 3: And the issue with Venus is that we had historically

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Speaker 3: simply just attributed the difference between Earth and Venus as

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Speaker 3: the fact that Venus is closer to the Sun. So

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Speaker 3: Venus is about thirty percent closer to the Sun than

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Speaker 3: the Earth is. And what this results in is that

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Speaker 3: Venus receives twice the amount of energy from the Sun

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Speaker 3: that the Earth does. And the assumption was that that

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Speaker 3: was the answer that simply, if you increase the amount

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Speaker 3: of sunlight that you receive by that amount, then it

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Speaker 3: pushes the planet down a different pathway into what we

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Speaker 3: refer to as a runaway greenhouse. However, there are many

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Speaker 3: other differences between Venus and Earth and just the amount

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Speaker 3: of energy that receives from the Sun. Because we also

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Speaker 3: know that Venus has a relatively little magnetic field. Earth

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Speaker 3: has a very very strong magnetic field. And in fact,

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Speaker 3: some of your listeners may know that we're currently going

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Speaker 3: through a period of solar activity which produces the fantastic auroras.

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Speaker 3: Is it, particularly if you're at northern or southern latitudes.

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Speaker 3: Then these are the results of the magnetic field interacting

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Speaker 3: with the solar wind. Venus doesn't really have a strong

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Speaker 3: magnetic field. We don't really understand why. Also, Venus has

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Speaker 3: a very very slow rotation. In fact, it rotates slightly

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Speaker 3: backwards because it takes two hundred and twenty five days

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Speaker 3: to go around the Sun, but it takes two hundred

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Speaker 3: and forty three days to rotate, So it takes longer

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Speaker 3: to rotate than it does to go around the Sun.

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Speaker 3: It's days longer than it's a year, and we don't

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Speaker 3: really understand why that is white effect that could have

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Speaker 3: had on its climate. Also, Venus doesn't have a substantial moon.

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Speaker 3: Earth has a substantial moon, which has had a very

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Speaker 3: large effect on the Earth's evolutionary history because of the

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Speaker 3: tidal effects that has on the Earth. Venus doesn't have that.

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Speaker 3: There are always these differences between Venus and Earth, and

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Speaker 3: we're not sure exactly which of those is the primary

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Speaker 3: cause or more likely a combination of these things in

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Speaker 3: causing Venus to not have habitable conditions. So Venus may

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Speaker 3: have had surface liquid water oceans just like the Earth,

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Speaker 3: and then it lost something. It lost it for example,

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Speaker 3: the reasons that Earth is able to maintain very nice

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Speaker 3: surface conditions. And in fact, many of my Earth's science

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Speaker 3: colleagues they say to me, you know, Stephen, one of

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Speaker 3: the most amazing things about the Earth is that it

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Speaker 3: has had surface liquid water for almost all of its history.

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Speaker 3: And that's an extraordinary thing because it means that the

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Speaker 3: temperature range has been between zero and one hundred degrees

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Speaker 3: for four and a half billion years. That is a

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Speaker 3: very difficult thing because everything's changing all the time, and

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Speaker 3: so how does the Earth do this? Well. One of

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Speaker 3: the ways that the Earth does this is it's able

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Speaker 3: to remove carbon dioxide from its atmosphere and it dissolves

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Speaker 3: into the ocean and it's removed via weathering on continents

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Speaker 3: when it rains, and that carbon is stored away in

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Speaker 3: the Earth's interior. Maybe Venus lost its ability to do that,

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Speaker 3: and so that it put the carbon the only place

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Speaker 3: it could, which is into its atmosphere, because its atmosphere

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Speaker 3: is about ninety six percent carbon dioxide, and so all

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Speaker 3: of its carbon dioxide has gone to its atmosphere. As

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Speaker 3: I said, we're not really quite sure why that happened,

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Speaker 3: how that happened, or when that happened, but it could

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Speaker 3: have been as recently as a billion years ago. It

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Speaker 3: could have been a billion years ago. It had oceans

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Speaker 3: just like the Earth.

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Speaker 2: I know Venus is the apple of your eye, but

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Speaker 2: let's shift to Mars for just a second, because the

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Speaker 2: same kind of questions have been asked about Mars. Mars

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Speaker 2: used to have an atmosphere, right, and we're now pretty

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Speaker 2: sure that there's ice on Mars, but it, you know it,

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Speaker 2: conditions for life could have been much different on Mars

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Speaker 2: a long time ago.

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Speaker 3: Correct, That's right. And it's actually quite the quite the

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Speaker 3: contrast when you look at Venus and you look at

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Speaker 3: Earth and you look at Mars, because as I mentioned earlier,

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Speaker 3: Venus's atmosphere is about one hundred times of the atmospheric

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Speaker 3: pressure of the Earth. Mars, on the other hand, is

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Speaker 3: about one percent of Earth's atmospheric pressure. Approblem, it's actually

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Speaker 3: less than that, it's more zero point six percent. That

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Speaker 3: means you've got a factor of ten thousand difference in

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Speaker 3: atmosphere pressure at the surface between Venus and Mars. And

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Speaker 3: so Mars has taken a very very different pathway. And

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Speaker 3: for Mars, we tend to attribute it that not necessarily

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Speaker 3: related to the distance from the Sun, but due to

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Speaker 3: its size, because one of the things that many people

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Speaker 3: don't fully appreciate is that Mars is significantly smaller than

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Speaker 3: the Earth. I say that because I have spoken to

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Speaker 3: many people in a public kind of forum and just

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Speaker 3: ask them how big do you think Mars is relative

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Speaker 3: to the Earth, And many people assume it's that they

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Speaker 3: know it's smaller, but they don't know it's that much smaller.

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Speaker 3: It's half the size that perhaps more importantly, it's only

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Speaker 3: about ten percent of Earth's mass. Ten percent of Earth's

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Speaker 3: mass means that its surface gravity is only about thirty

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Speaker 3: eight percent of Earth's surface gravity means that Mars has

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Speaker 3: a lot of trouble holding onto its atmosphere, and we

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Speaker 3: know this from observations that were made of Mars. There

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Speaker 3: is a NASA spacecraft called Maven which has been orbiting

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Speaker 3: Mars for some time and has been measuring the effect

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Speaker 3: of the solar wind on Mars. So the same kind

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Speaker 3: of effect that I mentioned earlier about the strong period

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Speaker 3: of solar activity we're going through at the moment that

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Speaker 3: produces beautiful auroras, that same kind of effect is devastating

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Speaker 3: to the Martian atmosphere because, like Venus, it doesn't have

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Speaker 3: much of a magnetic field, so it's exceptionally vulnerable and

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Speaker 3: a lot of the atmosphere is blown away. So Mars'

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Speaker 3: history may have had a reasonable atmosphere maybe half an

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Speaker 3: Earth's atmosphere worth of pressure at the surface soon after

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Speaker 3: it formed, which was sufficient for it to have surface

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Speaker 3: liquid water. And we know it surface liquid water because

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Speaker 3: we see all of the all of the evidence that

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Speaker 3: still exists today extremely well preserved, very clear that there

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Speaker 3: was liquid water moving around the surface of Mars, but

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Speaker 3: it probably wasn't able to retain it for very long,

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Speaker 3: in fact, only about five hundred million years at most,

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Speaker 3: and so it had a relatively short story when it

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Speaker 3: comes to having surface liquid water.

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Speaker 2: I read this story, it must be in the last

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Speaker 2: two or three weeks about the James Webb telescope discovering

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Speaker 2: an exo planet that had a magnetic field. And I

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Speaker 2: don't know if this is some salesmanship, some stephen Kin

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Speaker 2: type salesmanship on the part of those scientists, but they said, look,

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Speaker 2: it's got a magnetic field. It makes it more likely

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Speaker 2: that life could exist. Could you explain that to us

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Speaker 2: why that.

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Speaker 1: Is the case?

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Speaker 3: Yeah, this is somewhat of an unknown at the moment.

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Speaker 3: And you know, I currently operate in both exoplanets and

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Speaker 3: planetary science. That means that I spend a lot of

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Speaker 3: time looking for planets around other stars, and that is

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Speaker 3: primarily an exercise instellar astrophysics, because that's where the relationship

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Speaker 3: to the muse song starlight comes in. Because when we're

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Speaker 3: looking for exoplanets, what we're actually doing is looking very

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Speaker 3: very closely at the stars and trying to determine if

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Speaker 3: there's an object which is affecting it, which we call

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Speaker 3: an exoplanet. And then there's the planetary science side, which

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Speaker 3: is studying in great detail planets that we can actually

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Speaker 3: go there and visit and measure in our Solar System.

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Speaker 3: And the reason I mentioned that is because there's an

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Speaker 3: enormous information gap between those two fields, and so when

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Speaker 3: it comes to the magnetic field, it's something which is

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Speaker 3: still highly unknown as to the real effect of having

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Speaker 3: a magnetic field on a planet having long term habitability,

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Speaker 3: because we know that the magnetic field can help retain

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Speaker 3: an atmosphere in some respects, but it can also actually

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Speaker 3: be damaging, meaning that once again going back to the

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Speaker 3: effect of the aurora, that is, the charged particles from

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Speaker 3: the Sun being funneled into the poles into the Earth poles,

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Speaker 3: and that can actually increase the amount of atmospheric erosion

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Speaker 3: that's occurring in the polar regions, and so the jury

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Speaker 3: is still out actually as to whether having a strong

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Speaker 3: magnetic field is a good thing or a bad thing,

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Speaker 3: depending on all the other circumstances surrounding the planet. Now,

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Speaker 3: I will say that when we're talking about ex planet,

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Speaker 3: trying to determine if the planet has a magnetic field

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Speaker 3: is extremely difficult. It's not something that we can easily

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Speaker 3: measure from very large distances.

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Speaker 2: I would think. I mean, as you're looking at stars,

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Speaker 2: I forget it seems like that there's a term wobble.

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Speaker 2: Is that when you're that gives you the hint that

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Speaker 2: there's an exoplanet around a star.

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Speaker 3: Yes, that is one of the primary ways in which

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Speaker 3: we detect exoplanets, and that's due to the gravitational effect

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Speaker 3: that the planet has on the star. So it essentially

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Speaker 3: makes the star wobble. And so since that's a gravitational effect,

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Speaker 3: what we measure out of that is the mass of

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Speaker 3: the planet.

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Speaker 2: And does the web allow us to actually see those

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Speaker 2: exoplanets or we're still just guessing based on physics that

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Speaker 2: they're there.

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Speaker 3: Well, it's actually a combination of those two because, as

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Speaker 3: I mentioned earlier, most of the plan planets that have

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Speaker 3: been found have been discovered using what are referred to

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Speaker 3: as indirect techniques, but the real dream is to directly

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Speaker 3: detect them. That means take a picture and see the

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Speaker 3: light from the planet itself. That is still extremely hard

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Speaker 3: to do, and the gens web space telescope is not

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Speaker 3: particularly optimized towards that kind of work, although it has

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Speaker 3: done it already. There have been several announcements from gams

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Speaker 3: web where people have been able to observe a known

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Speaker 3: exoplanet and directly capture the light from the planet, but

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Speaker 3: that is extremely difficult to do can only happen for

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Speaker 3: a relatively small subset of the stars. The stars have

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Speaker 3: to be very close to us. Most of the planets

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Speaker 3: that we're talking about, and certainly the terrestrial planets like

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Speaker 3: Earth and Venus, these ones for the moment at least,

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Speaker 3: we still have to infer based on physics that those

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Speaker 3: planets are indeed dead.

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