Everything Everywhere Daily: History, Science, Geography & More - Asteroids

Starting point is 00:00:00 Our solar system is made up of a lot of things. The biggest thing is the sun, of course, which makes up the majority of the solar system's mass. And then we have the planets which come in various sizes and many of them have moons, also of various sizes. However, that isn't everything. There are other things in the solar system, things that amount to the debris between the much bigger objects. Learn more about asteroids, how they were discovered and how they might serve humanity's future. episode of Everything Everywhere Daily.

Starting point is 00:00:32 What if your perceptions about the past were wrong? ThruLine is a podcast that takes you back in time to uncover the parts of the story that may have gone unnoticed. It effectively turned day into night. And how it shaped the world now. Time travel with us every week on the ThruLine podcast from NPR. I've done many episodes on all of the major players in our solar system. I've covered every planet, the sun, and even the hypothetical planet X.

Starting point is 00:01:21 However, this doesn't make up the entire solar system. Floating around between the planets are smaller objects that are known as asteroids. The first question that we have to address is, what is an asteroid? If remember back to my previous episode on whether Pluto was a planet, astronomers have developed a definition to determine what is and what isn't a planet. There were three criteria which were said that had to be met for something to be called a planet. Number one, it is in orbit around the sun. Number two, it has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium.

Starting point is 00:02:01 In other words, it's nearly around. And finally, number three, it has cleared the neighborhood around its orbit. Asteroids do not meet all three of these definitions. All asteroids meet the first requirement in that they orbit the Sun. Some of them are large enough to meet the second requirement of having enough mass to be round-shaped. But no asteroid meets the third requirement, which is that they're big enough to clear out their orbit. In fact, as we'll see, asteroids are usually found with a whole bunch of other asteroids.

Starting point is 00:02:36 One thing that some of you might be thinking is what's the difference between an asteroid and a meteoroid? to the International Astronomical Union, the same group that created the definition of a planet, a meteoroid is, quote, a solid object moving in interplanetary space of a size considerably smaller than an asteroid and considerably larger than an atom, end quote. So that's a pretty vague definition, but we can probably safely say that if we can observe it from the surface of the Earth, then it's big enough to be called an asteroid. The discovery of asteroids actually took some time. It was what I would call a rather deliberate accident, and it involved a thing known as

Starting point is 00:03:18 the asteroid belt. The ancient people knew of the planets Mercury, Venus, Earth, Mars, Jupiter, and Saturn. By the late 16th century, astronomers had developed an idea of the distances of the planets from the sun. And once they had an idea of the distances, something seemed a bit off. The gap between Mars and Jupiter seemed abnormally large. The German astronomer Johannes Kepler analyzed the data collected by the Danish astronomer Tico Brahe and concluded, quote, between Mars and Jupiter, I place a planet. His guess was really just that, a guess based on his sense of proportion of the solar system. In the 18th century, Kepler's hunch developed into a much formal mathematical framework, a series of numbers that seemed to fit the distances of the planets was discovered.

Starting point is 00:04:14 It was first proposed by the astronomer Johann Titius and later refined by Johann Boda, both Germans. A law known as the Titius Boda law was named after them. The Titius Boda law states that if you take a sequence of numbers starting with zero and then go three, six, 12, 24, 48, etc. doubling the term each time. Then add four to each number and then divide it by 10, what you get is a close approximation to the distances of the planets from the sun in terms of astronomical units. The actual distance of all the planets from the sun up to Uranus is within 5% of the estimates provided by the Titius Boda law. However, there was a problem. There was a missing planet between Mars and Jupiter. The

Starting point is 00:05:06 Titius Boda law seemed to confirm the suspicion of Johannes Kepler from so many years before. It implied that a planet hadn't been found between Mars and Jupiter. The missing planet was apparently discovered by Gazepi Piazzi, an Italian Catholic priest on January 1st, 1801. The new planet was named Series, and at a distance of 2.8 astronomical units, it seemed to fit the Titius Boda law. Just before, I said that the discovery of the asteroid belt was a deliberate accident. It was deliberate insofar as people were looking for it in the rough orbit where it was found. It was an accident because it was later determined that the Titius Boda law was pretty much a pseudoscience.

Starting point is 00:05:53 The location of Neptune did not conform to the Titius Boda law at all, and there was no physical reason for it. It was just a series of numbers that happened to. conform to the orbit of the planets by sheer coincidence. The discovery of exoplanets around other stars has subsequently confirmed that the tinius Boda law has no scientific basis. Nonetheless, Series was discovered, but again there was something wrong. Astronomers started finding other things in the same orbit as series.

Starting point is 00:06:27 In 1802, Pallas was discovered in the same approximate orbit. This indicated that series wasn't the missing planet. Rather, it was something different. The astronomer William Herschel dubbed them asteroids. In 1804, Juno was discovered, and in 1807 Vesta. Throughout the 19th and early 20th centuries, a host of asteroids were found, each one seemingly smaller than the one before it. By 1921, over a thousand asteroids had been discovered. All of these minor planets were in a belt around the sun, which was dubbed the asteroid belt. People have some very mistaken views of the asteroid belt, mainly due to movies and television. It's often viewed as a region filled with rocks.

Starting point is 00:07:14 If you were a spacecraft trying to navigate the asteroid belt, it's often assumed that you'd have to be dodging rocks so they don't get hit constantly. That is not what the asteroid belt is like. If you were in the middle of it, odds are you would see absolutely nothing. Yes, there are objects in the asteroid belt, but they're spread so far apart that you couldn't possibly see one if you were on another asteroid. The current estimate is that there are 1.1 to 1.9 million asteroids larger than 1 kilometer and probably many million more that are smaller. Despite the seemingly large number of asteroids, they don't add up to very much.

Starting point is 00:07:54 All of the asteroids in the asteroid belt have less than 4% the, mass of our moon. The next big question with regards to the asteroid belt was how it was formed. One theory held that the asteroid belt was at one time the location of a planet, just as the titeous moda law suggested. According to the theory at some point in the early solar system, a Mars-sized planet or smaller either broke up or was destroyed. This theory has subsequently fallen out of favor because there isn't nearly enough mass

Starting point is 00:08:28 in the asteroid belt to have once compromised a planet the size of Mars. The current popular theory is that the material in the asteroid belt was simply never able to coalesce into a single object because of Jupiter's gravitational interference. Despite not being as sexy as the larger planets and moons in the solar system, asteroids continue to be studied, and it's a good thing that they were because what was found about them has groundbreaking potential. There are, roughly speaking, three categories. of asteroids, C-type, S-type, and M-type. C-type asteroids contain a high proportion of carbon

Starting point is 00:09:06 along with rocks and minerals. They are the most common, making up about 75% of known asteroids. S-type asteroids are made up of silicon materials and nickel-iron. These asteroids are less common. And finally, M-type asteroids are composed of mostly metallic iron and nickel and are relatively rare. It's the composition of these asteroids which has such enormous potential. If humans are ever going to build large-scale space stations or spacecraft, they're going to need an enormous amount of raw material to do so. These materials can't come from the Earth because of the difficulty and energy required

Starting point is 00:09:47 to get them out of the Earth's gravity well. Asteroids make for an almost perfect source of raw materials in space. They're rich in metals, and they're rich in metals. are millions of relatively small objects that could be towed in full wherever they're needed in the solar system. Asteroids are abundant and contain precious metals like platinum, gold, and rhodium, as well as rare earth elements that are used in electronics and other advanced materials. However, they also have abundant amounts of iron and nickel, as well as the most precious substance in space, water. The total economic value of asteroid mining is mind-blowing. A single

Starting point is 00:10:26 asteroid that was visited by a spacecraft was estimated to have an economic potential of $100,000 quadrillion dollars. To put that into perspective, the economic value of everything on Earth, including all the objects in real estate, is only somewhere between $400 trillion and $5 quadrillion, depending on the estimate you want to use. We're still a long way from asteroid mining, but asteroid exploration has already begun. A few missions have done flybys of asteroids, but they were only able to take quick images. To date, there has only been one mission to an asteroid

Starting point is 00:11:07 in the asteroid belt as an objective. In 2007, NASA launched the Dawn mission. It orbited the largest asteroid series, as well as Vesta, another very large asteroid. The Dawn mission was great, but what was really needed was a sample material. material from an asteroid. This finally took place in 2016 when NASA launched the Osiris mission. Osiris traveled to a near-Earth asteroid named 101-955 Benu. It was launched

Starting point is 00:11:39 on September 22nd, 2017, and arrived at Benu on December 3rd, 2018. It spent over two years analyzing the surface before landing on October 20th, 2020. It then took a sample of the asteroid and returned it to Earth. It arrived back to the Earth. on Earth with its sample on September 24, 2023. I should note that the asteroid belt is not the only place in the solar system with asteroids. Some have their own orbits around the sun, and other asteroids can be found in groups. The orbit of Jupiter has two groups of asteroids that have been captured and are now stuck in orbital resonance with Jupiter. Collectively, they are known as the Hildian asteroids. There are currently over 5,000 known Hildian asteroids that

Starting point is 00:12:25 gravitationally locked in Jupiter's orbit. The generic term for any asteroid that is gravitationally caught in a planet's Lagrange point is a Trojan asteroid. And there are probably millions more asteroids floating around the solar system that we are totally unaware of because we simply can't see them. Asteroids aren't as enchanting as planets. They don't have colorful atmospheres and there's certainly no possibility of life on them. But in terms of potential future usefulness. They might just be the most valuable things in the solar system. The executive producer of Everything Everywhere Daily is Charles Daniel. The associate producers are Benji Long and Cameron Kiever. I want to give a big shout out to everyone who supports

Starting point is 00:13:13 the show over on Patreon, including the show's producers. Your support helps me put out a show every single day. And also, Patreon is currently the only place where Everything Everywhere daily merchandise is available to the top tier of supporters. If you'd like to talk to to other listeners of the show and members of the Completionist Club, you can join the Everything Everywhere Daily Facebook group or Discord server. Links to everything are in the show notes.

Everything Everywhere Daily: History, Science, Geography & More - Asteroids

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