Ep. 644: Is Earth… Normal? (1)
Fraser: Astronomy Cast Episode 644: Is the Earth Normal? Welcome to Astronomy Cast, your weekly facts-based journey through the does cosmos. We hope you understand, not only what we know, but how we know what we know.
I'm Fraser Cain, the publisher of Universe Today. I've been a space and astronomy journalist for over 20 years. With me as always is Dr. Pamela Gay, the senior scientist for the Planetary Science Institute and the director of Cosmo Quest.
Hey, Pamela. How are you doing?
Dr. Gay: I am doing well. It is spring.
Fraser: Yeah.
Dr. Gay: We have tornados, but not today.
Fraser: Yes. So, I need to give the most…man, I don't even know how to describe this. I need to give the most weasel-word-ridden excitement potential thing to do coming up.
Dr. Gay: Okay, go for it.
Fraser: Okay. And so, that is that there is potentially, maybe, possibly the greatest meteor storm –
Dr. Gay: Yes.
Fraser: – in decades, maybe centuries happening on the evening of May 30th or the morning of the 31st depending on where you live.
Dr. Gay: Tau Herculids.
Fraser: The Tau Herculids meteor.
Dr. Gay: Get your hammock ready. Get your hammock ready.
Fraser: Yes. Yeah. What happened was this comet – and I'm not even gonna say the name, 73P – broke up in 1995. And the great Hubble has pictures of this.
Dr. Gay: Yeah.
Fraser: The comet expanded in brightness 400 times and tore itself apart. And we pass through the Tau Herculids every May 30th/31st every year. But this time it's possible that we're gonna be passing through the point where the comet broke up, and it all depends on the math.
But what that means is that we could see – like when you go and you watch the Perseid Meteor Shower during the summer and you have a really good time – you're like, “Woo-hoo,” – you're watching one meteor a minute, 60 meteors an hour.
Dr. Gay: Yeah.
Fraser: During a meteor storm like the '98 Leonids or the '66 Leonids, people were seeing upwards 1000 an hour. And I saw them, and they were absolutely incredible.
Dr. Gay: Yeah.
Fraser: So, some predictions for this storm are I've seen 10,000 an hour, 100,000 an hour. I've seen 40 meteors a second, which is 140,000 an hour. And with that comes a distribution of, not just regular meteors, but also fireballs and everything, bolides. It's just gonna be bonkers. But it's not certain.
Dr. Gay: Yeah.
Fraser: And so, it's going to be peaking at 10:00 p.m. Pacific Time on May the 30th, 1:00 a.m. Eastern Time, or 0500 Universal Time. And so, that means it's best positioned for North America, South America, a little bit of Europe. But I know people are like, “Oh no, I'm in Australia. Oh no, I'm in South Africa. Oh no.” Meteor storms are famously unpredictable.
Dr. Gay: Yeah.
Fraser: We get these kinds of warnings all the time, and they never show up. So, this almost certainly won't happen. But if it does, it'll be amazing. And it's almost certain that it'll be early or late. So, don't panic. Just on that night, go out. And if it's happening, we'll see a rise in meteor activity as you get closer and closer to the peak. And then the peak happens, and then we'll see declining meteors.
So, everyone on Earth should be able to get a shot at seeing this. Whether you're in the Northern Hemisphere, the Southern Hemisphere, in is for everybody. It could be the meteor storm of a generation, but it could also be nothing. So, don't yell at me.
Dr. Gay: This is an excuse to go camping if you like to go camping.
Fraser: Yeah.
Dr. Gay: This is an excuse to upgrade your hammock if you're thinking maybe this summer I need a better hammock.
Fraser: Yeah. Yeah.
Dr. Gay: We won't be recording next Monday.
Fraser: Yeah.
Dr. Gay: It is Memorial Day here in the US. But also, I plan to use this as an excuse to put more hammocks in the backyard, and have people over, and have a fire.
Fraser: More hammocks, yeah. Yeah. And even if you're in a city –
Dr. Gay: Yeah.
Fraser: – like if you're in the middle of a city, you'll still be able to see it.
Dr. Gay: Oh, bolides.
Fraser: Yeah, it'll be like, again, 40 a second. So, the sky's is gonna be just – it's gonna be raining stars. So, you'd see more in the dark if you're far away from the city lights, but you'll still see a lot if you're in a big city. So, this is for everybody. Everybody.
Dr. Gay: Yeah.
Fraser: And again, there's no guarantee this gonna happen. But the way I always say it is that you miss 100 percent of the meteor storms that you don't stand outside to watch.
Dr. Gay: It's true.
Fraser: So, don't blame me if you decide to not watch it and then it turns out to be the storm of the century.
Dr. Gay: Get your bug spray. Get an old AM/FM radio that you can toon in to hear them striking the atmosphere, and then tell us what you saw.
Fraser: Yeah. Awesome.
All right, we have done an episode about whether or not our solar system is normal. Now we wanna talk about our planet. We've now discovered thousands of exoplanets. We're learning more and more about the kinds of planetary systems that are out there across the universe. But are planets like Earth unique or totally rare?
So, when we think about this idea of is planet Earth normal, right, like we now know of many, many exoplanets out there. Are we getting a sense? Because I think in the past we would think in every star system there will be a Venus-like planet, and an Earth-like planet, and a Mars-like planet. There will be a terrestrial planet in the habitable zone of the star, and there could be life there.
Are we getting a sense of how similar Earth is to other kinds of terrestrial planets out there?
Dr. Gay: So, we're in this super weird time right now where we have started finding rocky worlds. We have started finding things that are roughly the size of Earth, but we can't find them around sun-like stars yet. So, we're only finding rocky worlds next to tiny, tiny stars that have tiny, tiny habitable zones right up next to their surface. So, we have found potentially habitable worlds that orbit every 11 days, while probably being tidally locked. And –
Fraser: Right.
Dr. Gay: Yeah.
Fraser: Experiencing flares from the red dwarf star.
Dr. Gay: But it's still encouraging because we've gone from this point where the first planet found around a normal star was found – it was a super-Jupiter snuggled up right next to its star, 51 Peg. And it was far hotter than we knew planets could exist. And so, we started out with this canonical idea prior to that of solar systems are gonna be rocky, rocky, rocky, gassy, gassy, icy, random stuff.
Fraser: Right.
Dr. Gay: And then we were like, oh no. It's hot Jupiter, hot Jupiter, and that was all we found. And then Kepler came along, and it was like, “No, no, wait. You were impatient,” and started finding other kinds of solar systems, leading us to understand we have no idea how solar systems are gonna form, and they're gonna do whatever they want and form however they want.
And the more we're able to see, the more we hope to be able to find that Earth 2.0 out there around that sun 2.0 star. But right now, we're kinda unique as far as we know.
Fraser: So, what can we learn about the kinds of terrestrial planets that have been found? And also, what do we know about the Earth and which factors we think might be contributing to us being maybe more unique? That's not really a word you should use. More special.
Dr. Gay: Special. Every child is special.
Fraser: Yeah.
Dr. Gay: That can mean so many things.
Fraser: You can't be more unique or less unique.
Dr. Gay: It's true.
Fraser: Either you're unique or you're not. That's all. Yeah.
Dr. Gay: It's true. So, what we're looking at is we still have this Goldilocks problem in our solar system of Venus is too hot, Mars is too cold, and we're just right. But our understanding of how we got here has evolved.
Mars doesn't have enough of a magnetic field, so it lost its atmosphere. But it once had oceans. Venus, it doesn't really have a magnetic field, all sorts of chaos went on other there. It has a super thick atmosphere. And we now think that something catastrophic occurred anywhere from a few million to a few hundred million years ago that took it from being an ocean world to being what we see today, and that's a bit terrifying to think about.
Fraser: Were those Venus and Mars problems as opposed to habitable zone problems?
Dr. Gay: Those were Venus and Mars problems as opposed to habitable world problems.
Fraser: Yeah. Right. So, if Venus had a different atmosphere composition or a different mass, it could be as habitable as Earth, and even same with Mars –
Dr. Gay: Yeah.
Fraser: – if it had maybe a thicker atmosphere but a lot more mass. There could have been three completely habitable worlds in the Solar System if you just fine tuned their chemicals a little bit.
Dr. Gay: Yeah. Mars, you'd have to like change its mass to allow it to –
Fraser: Yeah. No, the same mass as Earth. If Mars was the same mass as Earth –
Dr. Gay: Yeah.
Fraser: – Venus was the same mass as Earth –
Dr. Gay: Oh, right.
Fraser: – Venus had maybe a thinner atmosphere than Earth, Mars had a thicker atmosphere than Earth, you could probably balance out all three in terms of energy budget.
Dr. Gay: And I think the rotation rate is something we also have to pay attention to with Venus. Because Venus somehow got flipped upside down rotationally.
Fraser: Right.
Dr. Gay: And it's rotating so slowly that its day exceeds its year. And that changes the mixing that's able to go on in its core. So, had the sets of collisions that occurred in our solar system been different, had that Mars-sized world that hit the proto-Earth maybe hit the proto-Mars and made something much bigger, had wherever hit Venus not hit at the angle it hit at and changed its rotation it way it did, it could have been a completely different scenario.
And we're still trying to figure out even the role Earth's moon has. There are some ideas that without Earth's moon and the tidal forces it puts on our world, we might not have been able to support life the way that we do today. And so, there's all of these what ifs. And until we're able to start consistently finding and studying smaller worlds around sun-like stars where that habitable zone is further out and you're not getting tidally locked, it's just computer models all the way down.
Fraser: Right. It is interesting how we've got these other examples just in our solar system how things can go wrong and make planets that are uninhabitable today.
Dr. Gay: Yes.
Fraser: Where with Venus, no planet-wide magnetosphere, a horribly thick atmosphere of carbon dioxide, sulfuric acid, intense temperatures and pressures.
Dr. Gay: It personifies death from the skies.
Fraser: Yeah. Yeah, it's hell.
Dr. Gay: Yes.
Fraser: And then on Mars, low mass, dead interior, not a thick enough atmosphere, couldn't hold onto its atmosphere, etc., etc. And then with Earth, we've got a large moon keeping us stable, but also probably no giant impact that rolled us over on our side since the moon.
