The 5 Greatest Mysteries Our Solar System Still Can't Explain

Added: 2026-05-10

[00:00:00]What if everything we thought we knew about our own cosmic neighborhood was wrong?

[00:00:05]Not about distant galaxies or stars billions of light years away, but right here in our own solar system.

[00:00:12]The one we've studied for centuries. It turns out there are five things happening in our own backyard that science simply cannot explain. For decades we've built extraordinary detailed models of how our solar system formed. A young star surrounded by a spinning disk of gas and dust. Gravity pulling materials together, planets growing, migrating, settling into orbits. The story seemed almost complete. A few loose ends here and there, nothing to lose sleep over. But as our telescopes got sharper and our probes got closer, the loose ends didn't resolve. They multiplied. Five of them are so strange, so defiant of our best models, that some scientists now wonder if we're missing something fundamental.

[00:01:00]Something that could rewrite our understanding of how the solar system works.

[00:01:05]Mystery number one. Something out there is pulling.

[00:01:10]Beyond Neptune, at the cold, dark edge of our solar system, lies the Kuiper Belt. A vast ring of icy objects and dwarf planets including Pluto.

[00:01:21]Astronomers studying these objects noticed [music] something deeply strange. A cluster of them share orbits that defy probability. Tilted, stretched, and pointed in the same direction.

[00:01:34]As if something massive is pulling them.

[00:01:37]The math is clear. There is another planet out there. Scientists call it Planet Nine. Imagine a world roughly the size of Neptune, orbiting so far from the sun that a single year there would last between 10,000 and 20,000 Earth years. A frozen, lightless world where the sun looks like little more than a bright star. We haven't seen it, not once, but we know something is there because of the gravitational fingerprint it leaves on everything around it. The universe is pointing at something we simply cannot find. Mystery number two.

[00:02:10]The Late Heavy Bombardment.

[00:02:14]Around 3.9 billion years ago, something happened. The inner solar system was suddenly bombarded by a catastrophic wave of asteroids.

[00:02:24]An event that scientists call the Late Heavy Bombardment.

[00:02:28]Look at the moon's surface. Every crater you can see from your backyard tells part of this story. The question is why?

[00:02:35]What disturbed the asteroid belt so violently? Why then not earlier?

[00:02:41]The leading theory points to Jupiter and Saturn. As these giants migrated slightly in their orbits, their gravity destabilized vast regions of the asteroid belt, flinging debris inward like a cosmic [music] pinball machine.

[00:02:55]Rocks hundreds of miles across raining down on early Earth.

[00:02:59]And yet life [music] survived.

[00:03:02]Not only that, some scientists believe this bombardment may have delivered the organic molecules that sparked [music] life itself.

[00:03:10]The event that nearly destroyed everything may be the reason we exist.

[00:03:14]We just can't fully prove it.

[00:03:17]Mystery number three.

[00:03:19]Venus. This planet should be Earth's twin >> [music] >> and somehow became its nightmare. Venus, same size, same mass, same rough distance from the sun.

[00:03:30]On paper, it should be another Earth, maybe even a living one.

[00:03:34]Instead, its surface [music] temperature is 465 degrees Celsius, hot enough to melt lead. Its atmospheric pressure is 90 times greater than ours and it rains sulfuric acid. Here's what no one can explain. Venus should have plate tectonics. The internal heat, the size, the composition, everything in our models says it should work exactly like Earth, but there's no evidence it does.

[00:03:59]Instead, Venus appears to have been completely resurfaced, wiped clean [music] in a single catastrophic volcanic event roughly 700 million years ago. Imagine if every continent on Earth sank, every ocean evaporated, and molten rock covered every surface on the planet simultaneously.

[00:04:18]Venus is our closest neighbor, and it remains as the most mysterious world in our solar system. If you're finding these mysteries as fascinating as we do, make sure you hit that like and subscribe button down below. We explore the universe's biggest questions every week. Now, two more mysteries to go, and the last might be the strangest of all.

[00:04:37]Mystery number four [music] is easy to miss, but once you see it, you can't unsee it. At the outer edge of the Kuiper [music] Belt, the population of objects drops off sharply, not gradually, [music] not the way you'd expect from materials thinning out over billions of miles.

[00:04:54]>> [music] >> It stops like a wall. Scientists call it the Kuiper Cliff. Every model predicts a gradual fade. Instead, there's an abrupt boundary, as if something [music] swept through and cleared everything beyond it. Something planet-sized. Something we haven't found. And mystery number five, the one that touches everything including us, is water. 71% of Earth's surface is covered with liquid water.

[00:05:21]Where did it come from? Earth formed too close to the young sun for water ice to survive. It should have been baked away during formation, so it arrived later, delivered by something.

[00:05:33]The leading candidates are asteroids and comets, and we've found evidence certain asteroids carry water-bearing materials with chemical signatures that match our oceans. Roughly is the problem, the chemistry [music] isn't a perfect match.

[00:05:48]Comets carry abundant water, but their isotopic signature doesn't match Earth's seas, either. We know the water arrived, but we just don't know exactly how or from where, or how Earth ended up with so much of it while Mars and Venus ended up dry.

[00:06:05]This isn't just speculation. The James Webb Space Telescope is actively studying the outer solar system right now.

[00:06:13]The Vera Rubin Observatory will survey the Kuiper Belt with unprecedented precision, potentially spotting Planet Nine signature.

[00:06:22]Missions like Europa Clipper and Dragonfly are heading toward the moons of Jupiter and Saturn, hunting for answers to some of these very same questions.

[00:06:31]The golden age of solar system exploration isn't behind us. It's happening right now. These five mysteries aren't just scientific puzzles. They're a reminder that the universe doesn't give up its secrets [music] easily, even the ones closest to home.

[00:06:46]We may have a ninth planet orbiting in the darkness right now. We may still not fully understand how our own water got here, and somehow that makes the sky feel a little bigger and a little stranger. Thanks for watching. If you want to be a part of the next space adventure, make sure you hit that like and subscribe button down below. And as always, keep looking up.