Now here's a highlight from Coast to coast am on iHeartRadio. Stephen.
I know, I recall from reading my UFO history that back in the fifties had these writers who told the public that they'd met people from Venus. They said they even took quick trips to Venus aboard spaceships, and those Venusians, I would think, would have to have pretty thick skin to survive the conditions there. I mean, is it the hottest planet as I've seen it described, hotter than Mercury, which as far as I know, is much closer to the Sun.
Yes, indeed, it is hotter than mercury, which seems extraordinary given as you said that Mercury is closer to the Sun. But of course it's all to do with its atmosphere. Venus has an extraordinary atmosphere. It's extraordinarily complicated, and that is a big part of the puzzle about understanding that. So not just so that we can understand planets around other stars, but understand what this could mean for Earth,
for example, about the future of Earth. But as you indicated earlier, it's possible that Venus was not always like it currently is. One of the things I always emphasize when I'm speaking to people about this, is that it's very important to remember that when we look at the Solar System, whether we're looking at Jupiter or Venus or even Earth, we're looking at these objects at an age
of four and a half billion years. That is a lot of history behind them that we try and learn about as best we can, and a lot of effort goes on for the Earth in that respect, of course, but with Venus it's a similar kind of thing. Venus has had a whole story to evolve there, and what we try and do is uncover that story because it may have had a past history that looked not too
dissimilar from the Earth. And in fact, when we looked at the Solar system when the Solar System was only two billion years old as an alien civilization, imagine that we're looking at our solar system two billion years ago. Then we may have concluded that there were two Earth sized planets, both of them with oceans. And that's quite profound because it means that that there could have been a much better chance for life in our Solar system
back then. But it also tells us that planets can change in very dramatic ways during their history, and so the big challenge for us is how does that happen, Why does that happen? And when does that happen?
Yeah, was Venus a long ago more like Earth today? Or was Earth now or long ago more like Venus today? Or have both of them changed? I guess there's probably the more likely answer.
Well, I guess this goes back to the nomenclature that you mentioned that we often refer to Venus as being a twin and if we follow that reasoning a little further, what this implies is that they certainly formed at the
same time four and a half billion years ago. They probably formed under very similar conditions and out of very similar kinds of material, and so there probably are a lot of similarities between them if we were to look them at the Earth and Venus when they were both extremely young, and so they probably started on very similar tracks in the way in which their atmospheres were forming, the way in which the planets were initially cooling these surfaces we have been in a magma state as they
were cooling off from formation. The question is what happened then, And the issue with Venus is that we had historically simply just attributed the difference between Earth and Venus as the fact that Venus is closer to the Sun. So Venus is about thirty percent closer to the Sun than the Earth is. And what this results in is that Venus receives twice the amount of energy from the Sun
that the Earth does. And the assumption was that that was the answer that simply, if you increase the amount of sunlight that you receive by that amount, then it pushes the planet down a different pathway into what we refer to as a runaway greenhouse. However, there are many other differences between Venus and Earth and just the amount of energy that receives from the Sun. Because we also know that Venus has a relatively little magnetic field. Earth
has a very very strong magnetic field. And in fact, some of your listeners may know that we're currently going through a period of solar activity which produces the fantastic auroras. Is it, particularly if you're at northern or southern latitudes. Then these are the results of the magnetic field interacting with the solar wind. Venus doesn't really have a strong magnetic field. We don't really understand why. Also, Venus has
a very very slow rotation. In fact, it rotates slightly backwards because it takes two hundred and twenty five days to go around the Sun, but it takes two hundred and forty three days to rotate, So it takes longer to rotate than it does to go around the Sun. It's days longer than it's a year, and we don't really understand why that is white effect that could have had on its climate. Also, Venus doesn't have a substantial moon.
Earth has a substantial moon, which has had a very large effect on the Earth's evolutionary history because of the tidal effects that has on the Earth. Venus doesn't have that. There are always these differences between Venus and Earth, and we're not sure exactly which of those is the primary cause or more likely a combination of these things in causing Venus to not have habitable conditions. So Venus may have had surface liquid water oceans just like the Earth,
and then it lost something. It lost it for example, the reasons that Earth is able to maintain very nice surface conditions. And in fact, many of my Earth's science colleagues they say to me, you know, Stephen, one of the most amazing things about the Earth is that it has had surface liquid water for almost all of its history. And that's an extraordinary thing because it means that the temperature range has been between zero and one hundred degrees
for four and a half billion years. That is a very difficult thing because everything's changing all the time, and so how does the Earth do this? Well. One of the ways that the Earth does this is it's able to remove carbon dioxide from its atmosphere and it dissolves into the ocean and it's removed via weathering on continents when it rains, and that carbon is stored away in
the Earth's interior. Maybe Venus lost its ability to do that, and so that it put the carbon the only place it could, which is into its atmosphere, because its atmosphere is about ninety six percent carbon dioxide, and so all of its carbon dioxide has gone to its atmosphere. As I said, we're not really quite sure why that happened, how that happened, or when that happened, but it could have been as recently as a billion years ago. It
could have been a billion years ago. It had oceans just like the Earth.
I know Venus is the apple of your eye, but let's shift to Mars for just a second, because the same kind of questions have been asked about Mars. Mars used to have an atmosphere, right, and we're now pretty sure that there's ice on Mars, but it, you know it, conditions for life could have been much different on Mars a long time ago.
Correct, That's right. And it's actually quite the quite the contrast when you look at Venus and you look at Earth and you look at Mars, because as I mentioned earlier, Venus's atmosphere is about one hundred times of the atmospheric pressure of the Earth. Mars, on the other hand, is about one percent of Earth's atmospheric pressure. Approblem, it's actually less than that, it's more zero point six percent. That means you've got a factor of ten thousand difference in
atmosphere pressure at the surface between Venus and Mars. And so Mars has taken a very very different pathway. And for Mars, we tend to attribute it that not necessarily related to the distance from the Sun, but due to its size, because one of the things that many people don't fully appreciate is that Mars is significantly smaller than
the Earth. I say that because I have spoken to many people in a public kind of forum and just ask them how big do you think Mars is relative to the Earth, And many people assume it's that they know it's smaller, but they don't know it's that much smaller. It's half the size that perhaps more importantly, it's only
about ten percent of Earth's mass. Ten percent of Earth's mass means that its surface gravity is only about thirty eight percent of Earth's surface gravity means that Mars has a lot of trouble holding onto its atmosphere, and we know this from observations that were made of Mars. There is a NASA spacecraft called Maven which has been orbiting Mars for some time and has been measuring the effect
of the solar wind on Mars. So the same kind of effect that I mentioned earlier about the strong period of solar activity we're going through at the moment that produces beautiful auroras, that same kind of effect is devastating to the Martian atmosphere because, like Venus, it doesn't have much of a magnetic field, so it's exceptionally vulnerable and
a lot of the atmosphere is blown away. So Mars' history may have had a reasonable atmosphere maybe half an Earth's atmosphere worth of pressure at the surface soon after it formed, which was sufficient for it to have surface
liquid water. And we know it surface liquid water because we see all of the all of the evidence that still exists today extremely well preserved, very clear that there was liquid water moving around the surface of Mars, but it probably wasn't able to retain it for very long, in fact, only about five hundred million years at most, and so it had a relatively short story when it comes to having surface liquid water.
I read this story, it must be in the last two or three weeks about the James Webb telescope discovering an exo planet that had a magnetic field. And I don't know if this is some salesmanship, some stephen Kin type salesmanship on the part of those scientists, but they said, look, it's got a magnetic field. It makes it more likely that life could exist. Could you explain that to us why that.
Is the case?
Yeah, this is somewhat of an unknown at the moment. And you know, I currently operate in both exoplanets and planetary science. That means that I spend a lot of time looking for planets around other stars, and that is primarily an exercise instellar astrophysics, because that's where the relationship
to the muse song starlight comes in. Because when we're looking for exoplanets, what we're actually doing is looking very very closely at the stars and trying to determine if there's an object which is affecting it, which we call an exoplanet. And then there's the planetary science side, which is studying in great detail planets that we can actually go there and visit and measure in our Solar System.
And the reason I mentioned that is because there's an enormous information gap between those two fields, and so when it comes to the magnetic field, it's something which is still highly unknown as to the real effect of having a magnetic field on a planet having long term habitability, because we know that the magnetic field can help retain an atmosphere in some respects, but it can also actually be damaging, meaning that once again going back to the
effect of the aurora, that is, the charged particles from the Sun being funneled into the poles into the Earth poles, and that can actually increase the amount of atmospheric erosion that's occurring in the polar regions, and so the jury is still out actually as to whether having a strong magnetic field is a good thing or a bad thing,
depending on all the other circumstances surrounding the planet. Now, I will say that when we're talking about ex planet, trying to determine if the planet has a magnetic field is extremely difficult. It's not something that we can easily measure from very large distances.
I would think. I mean, as you're looking at stars, I forget it seems like that there's a term wobble. Is that when you're that gives you the hint that there's an exoplanet around a star.
Yes, that is one of the primary ways in which we detect exoplanets, and that's due to the gravitational effect that the planet has on the star. So it essentially makes the star wobble. And so since that's a gravitational effect, what we measure out of that is the mass of the planet.
And does the web allow us to actually see those exoplanets or we're still just guessing based on physics that they're there.
Well, it's actually a combination of those two because, as I mentioned earlier, most of the plan planets that have been found have been discovered using what are referred to as indirect techniques, but the real dream is to directly detect them. That means take a picture and see the light from the planet itself. That is still extremely hard to do, and the gens web space telescope is not particularly optimized towards that kind of work, although it has
done it already. There have been several announcements from gams web where people have been able to observe a known exoplanet and directly capture the light from the planet, but that is extremely difficult to do can only happen for a relatively small subset of the stars. The stars have
to be very close to us. Most of the planets that we're talking about, and certainly the terrestrial planets like Earth and Venus, these ones for the moment at least, we still have to infer based on physics that those planets are indeed dead.
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