The next time you look up at a bright full moon, think about this: No one knows exactly where the moon came from.
“We have no idea why the moon is here,” science writer Rebecca Boyle continues inexplicable – Vox’ podcast exploring great mysteries, unanswered questions and all things we learn by diving into the unknown. “I think for a lot of people [the moon] is taken for granted, it’s everyday things like this, and galaxies and nebulae and stars and planets are more intriguing.”
It’s true that some of the most epic questions in science are found in the farthest reaches of space — how and when did the first galaxies form, what happens in a black hole — but equally epic questions exist here in ours. heavenly environment, in our own solar system.
Exploring our own solar system — the moons and planets in it — is to better understand what’s possible in the farthest reaches of the universe. Anything we find or discover in our own cosmic backyard will help us understand what is possible in the wider universe. If evidence of ancient life is found on a hostile world like Mars, we may be able to better understand how common life might be in other solar systems. Understanding how a possibly once-vibrant world like Venus went into decline may help us understand how often similar planets around other stars die in an apocalypse.
The solar system’s most provocative mysteries help us understand why we’re here, how much longer we might have, and what we might leave behind. Here are some of the mysteries of the solar system we encountered on inexplicable†
Listen and follow for more mysteries inexplicable wherever you listen to podcasts†
What killed Venus?
“Hellscape” is the most appropriate word to describe the surface of Venus, the second planet from the sun. At 900 degrees Fahrenheit, it is the hottest planet in the solar system, thanks to an atmosphere made up almost entirely of carbon dioxide, generating a very strong greenhouse effect. Clouds of highly corrosive sulfuric acid drape over a volcanic landscape of razor-sharp volcanic rock. The pressure on the surface of Venus is about 92 times what you would feel at sea level on Earth.
Still, some scientists suspect that Venus was once much like Earth, with an ocean of liquid water, like the one that supports life on our planet. This raises an existential question for life on Earth.
“Venus and Earth are planetary siblings,” said Robin George Andrews, volcanologist and author of Super volcanoes: what they reveal about Earth and the worlds beyond† “They are made at the same time and made of the same material, but Venus is apocalyptic and terrible in every way. Earth is a paradise. So why do we have a paradise next to a lost paradise?”
There are two leading hypotheses. One is that the sun boiled Venus to death. The other is that volcanoes did.
Read further: Venus could have been a paradise, but turned into a hellscape. Earthlings, take note.
Where does the moon come from?
Before the moon landings, scientists thought they knew how the moon was formed. The prevailing theory was that it formed just like the planets: bits of material left over from the formation of the sun fell together. But then Apollo astronauts brought back samples from the lunar surface, and those rocks told a very different story.
“Geologists had discovered that the moon was covered with a special kind of rock called anorthosite,” inexplicable senior producer Meradith Hoddinott explains about the show. “Glistening, clear and reflective, this is the rock that makes the moon shine white in the night sky. And at the time it was thought that this rock can only be formed in a very specific way. Magma.”
But magma means the moon must have formed in some sort of epic disaster. “Something that flowed so much energy into the moon that it literally melted,” Hoddinott says. Scientists don’t know exactly how it all ended. But each screenplay is a cinematic tale of fiery apocalyptic proportions.
Read further: How Apollo Moonstones Reveal the Epic History of the Cosmos
Is there anything alive in the human poo left on the moon?
During the Apollo moon missions, astronauts went to the moon and to save weight for the return to Earth, they dumped their waste behind. Astronauts departed on all Apollo missions 96 bags of human waste on the moon, and they pose a fascinating astrobiological question.
Human waste – and feces in particular – teems with microbial life. With the Apollo moon landings, we brought microbial life on Earth to the most extreme environment it has ever been in. Which means the garbage on the moon represents a natural, if unintentional, experiment.
The question the experiment could answer: How resilient is life in the face of the moon’s unforgiving environment? And by the way, if microbes can survive on the moon, can they be interplanetary or… interstellar travel† If they can survive, it may be possible for life to spread from planet to planet, riding on the backs of asteroids or other such space junk.
Read further: Apollo astronauts left their poop on the moon. We gotta get back for that shit.
Was there an advanced civilization on Earth before humans?
Many scientists have long wondered: is there intelligent life in the deep reaches of space? But climate scientist Gavin Schmidt and astrophysicist Adam Frank have a different question: Was there intelligent life in the deep reaches of Earth’s history? Can we find evidence of an advanced non-human civilization that may have lived hundreds of millions of years ago, buried in the Earth’s crust?
This is not strictly a “solar system” mystery, but it has cosmic scope. At their core, Schmidt and Frank ask: How likely is it that an intelligent life form on a planet—here or in the deepest reaches of space—leave a sign, a sign that they existed? And by the way, in hundreds of millions of years, some alien explorers landing on Earth will be able to find traces of humans when we’re long, long gone?
Read further: The Silurian hypothesis: could it be possible to discover an industrial civilization in the geological record?
Can we push an asteroid off a collision course with Earth?
Many disasters – volcanic eruptions, earthquakes, hurricanes, tornadoes – are inevitable. Scientists talk about when, not if, they will strike. While humans exacerbate some disasters, natural disasters have occurred long before we were here. They are a fact of life on Earth. But one kind of disaster need not be inevitable: a collision between an asteroid or comet and Earth.
The problem is, we’ve never tried to deflect an asteroid, and we don’t know if a plan to do that would work.
To help answer this question, NASA last year launched the Double Asteroid Redirection Test (DART), a car-sized box equipped with solar panels. It is currently on its way to a 160 meter long asteroid called Dimorphos. In the fall, DART Dimorphos will crash at 24,000 kilometers per hour (about 15,000 miles per hour) to answer a big question: Could the collision push the asteroid into a slightly different orbit?
Read further: The quest to avert an asteroid apocalypse is going surprisingly well
Was there ever life on Mars?
Mars today is a desert, devoid of obvious signs of life. But over the years, scientists have found evidence of a long-ago lost Mars that might have looked much more like Earth.
“Mars is a very different place today than it was 4 billion years ago, but you can see evidence of what it was like,” said NASA astrobiologist Lindsay Hays. “You see things like the remains of a huge river delta, which indicates that not only was water flowing, but you probably had a lot of water flowing over a long period of time that continued to deposit sediments.”
And where there was water, there could have been life. Last year a new rover landed on Mars, and it’s our best chance at answering the question, “was there ever life on Mars?” If the answer is yes, it could change our understanding of how life occurs in the universe.
The inexplicable episode on Mars aired on June 22.
Read further: NASA’s newest rover is our best chance yet to find life on Mars
Is there a real ninth planet lurking in the darkness?
In 2006, the International Astronomical Union voted to change the definition of what a planet is, and Pluto didn’t make it. There were no longer nine official planets in the solar system, but eight.
But then “we started getting these hints that there really is something else out there — and a real giant planet that we think is still lurking far beyond Neptune, waiting to be found,” astronomer Mike Brown says of inexplicable† Astronomers have yet to discover this planet, but they suspect it is there: other objects far away in the solar system appear to be affected by gravity.
Could these hints lead us to a real new ninth planet? Could be. But it will be hard to find.
“It’s like taking a little black grain of sand and throwing it on the beach,” Brown says of the quest. “That would be a little hard to find in the sea of all the others. And that’s the problem with Planet Nine.”
Read further: The hunt on planet 9
If you have ideas for topics for future shows, please email us at firstname.lastname@example.org.