BAN #261: Podcast interviews on mistakes and dinosaurs, Bits of Venus on the Moon
12 October 2020 Issue #261
|Oct 12, 2020||2|
[Spiral Galaxy M81 image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona]
Subscribers will never go extinct
Upcoming Appearances/Shameless Self-Promotion
Where I’ll be doing things you can watch and listen to or read about
I was recently interviewed by Katie Davis for a podcast called Fehler, which is German for error. We talked about making mistakes in science, and why they’re important. At least, how learning from them is important.
It’s somewhat similar to my TED talk on the topic, though it goes in a different direction.
So go, and don’t be afraid of making mistakes! Accept that they happen. And learn from them.
Upcoming Appearances/Shameless Self-Promotion
Yes, another one
In a slightly different tone, I chatted with my old friend Iszi Lawrence and Dr. David Hone about the asteroid that killed the dinosaurs, the Chelyabinsk impact, and what we would do if we saw a big rock headed our way now — including the odds of that happening. This is all part of their fun podcast Terrible Lizards, which you will note is somewhat lighter in feel than Fehler.
I’ve known Iszi a long time, and she’s a delight, so this was a lot of fun to do. We talked for WAY over an hour, and they only used the first half of what we talked about. I’m hoping they eventually find a place for the second part, because I grilled Dr. Hone on dinosaurs, and learned a lot from him.
[Iszi Lawrence and me way back in 2009 at the TAM London meeting. I was not in a ditch, nor was she on a step above me. She’s just really long. The hair helps.]
What I’ve recently written on the blog, ICYMI
[NGC 2525 is a spiral galaxy 70 million light years away. In 2018, the light from a supernova in it reached Earth, allowing astronomers to better understand how white dwarf stars explode. From Tuesday’s article. Credit: ESA/Hubble & NASA, A. Riess and the SH0ES team. Acknowledgment: Mahdi Zamani]
Monday 5 October, 2020: A second planet for Beta Pic confirmed!
Tuesday 6 October, 2020: Amazing video: Hubble watches as a catastrophic stellar explosion fades
Wednesday 7 October, 2020: If you want to disprove Einstein, it just got 500 times harder
Thursday 8 October, 2020: Sailing the lakes of Titan? Prepare for rough seas.
Friday 9 October, 2020: Martian eclipses can be detected on a lander’s… seismograph?
A brief synopsis of some interesting astronomy/science news
Alternate title: Venus on the lunar mountaintop
Venus is a pain.
Its atmosphere is so thick it’s hard to examine its surface (and landers there have a tendency to be crushed and melt after an hour or two since the pressure is 90 Earth atmospheres and the temperature is high enough to melt lead and tin). Also, it’s closer to the Sun than Earth, which makes it hard to get spacecraft to it; they need a big boost to catch up to the planet, which orbits the Sun more rapidly.
But it might be easier to study it than previously thought. A paper just came out saying that if we want to find pieces of Venus, we should look on the Moon.
That’s not as silly as it sounds. In fact, it makes sense.
[Artwork of Venus getting slammed by a comet long ago. Credit: Sam Cabot]
When the giant dinosaur-killer asteroid hit Earth 66 million years ago and made a crater 200 kilometers wide, as much as 12% of the material was ejected fast enough to escape the Earth entirely. That material is long gone, though it’s possible some of it is on the Moon. I’ll note that a rock brought back from the Apollo 14 mission may contain pieces of Earth rocks in it, lodged there from ancient terrestrial impacts.
So why not Venus? If a giant impact happened today, it’s likely most if not all the ejecta would be stopped by Venus’s ridiculously thick atmosphere. But we also know that Venus had more water on its surface and in its air long ago, possibly as recent as 700 million years ago. It was after then that something happened to trigger a massive outgassing of carbon dioxide in its air leading to a runaway greenhouse effect.
That means the atmosphere of Venus was much thinner before that point, because we know the surface wasn’t nearly as hot (or else we wouldn’t find the evidence of ancient water). So a giant impact before that point in time could have launched a substantial amount of Venusian material into space. These happen roughly every hundred million years, so there have been plenty of opportunities. And smaller impacts could still eject material into space, and in fact a lot of the rocks won’t be hugely altered; the temperatures and pressures in some parts of the impact are low enough that the rocks will be largely intact mineralogically.
Getting it to Earth is difficult — getting rocks up and away, farther from the Sun, also takes a lot of energy — but the authors of the paper find it’s not only possible, but actually a rather efficient process. It works especially well if an asteroid or comet hits Venus head on, on the side of Venus facing into its orbital direction. That makes sense; the velocities add together giving ejected material more energy, just like a head-on collision on the road does more damage than one where someone rear-ends you.
They simulated various impact scenarios, following up with orbital trajectories, and found that as much as a million kilograms (1000 tons) of only mildly shocked Venusian rocks may be on the Moon. Giant impacts on Venus were more common more than 3.5 billion years ago, and that material would be buried pretty deep (up to a kilometer) on the Moon, but more recent impacts would leave material closer to the Moon’s surface, mixed in with material just a few meters deep. They estimate that Venusian material will make up about 0.2 parts per million of material on the Moon, and much of it would impact slowly enough that they would remain chemically intact.
That’s tiny, but could in practice be possible to find. That’s interesting, and useful! We don’t know when Venus got hot and lost its water, but that information could be locked up in rocks on the Moon. If enough samples were obtained from enough different times in the past, a rough timeline of the history of Venus could be obtained. That would be incredibly helpful in understanding why Venus went from being relatively Earth-like to the hellhole it is now.
I’ll note that many more rocks fell on Earth, but our active crust and erosive atmosphere will have destroyed those meteorites long ago. On the Moon, they may yet be intact. And going to Venus won’t help; the surface gets repaved pretty often due to volcanic activity, so finding an intact geological record there is likely impossible. The Moon is easier to reach, and easier to sift through.
Not that it’s easy. Venusian rocks will have to excavated, and rocks examined carefully. It’s a big project, but one that could be done once there’s a decent human presence on the Moon. So this may be a while — decades, certainly. But Venus has been around 4.6 billion years. I guess it can wait a little longer to reveal its watery secrets.
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