What’s the weirdest planet in the solar system?

The UniverseFridays

April 17, 2026

5 min read

Add Us On GoogleAdd SciAm

What’s the weirdest planet in the solar system?

All the sun’s planets are oddballs. But some are more so than others

By Phil Plait edited by Lee Billings

An illustration of our solar system showing the planets far closer together than they are in reality in order to represent the all of the bodies with some detail.

NASA/JPL-Caltech

Stay connected to The Universe: Get email alerts for this weekly column by Phil Plait

Enter your email

I agree my information will be processed in accordance with the Scientific American and Springer Nature Limited Privacy Policy. We leverage third party services to both verify and deliver email. By providing your email address, you also consent to having the email address shared with third parties for those purposes.

Sign Up

Even at a glance, the planets in our solar system are wildly diverse. Huge and small, airless and densely packed with atmosphere, they have a wide range of characteristics distinguishing them. But if I was backed into a corner, which one would I choose as the oddest of them all?

Easy: Venus is the weirdest planet in the solar system.

There’s a reason we call it Earth’s evil twin. For reasons that are still unclear, long ago it suffered a massive runaway greenhouse effect, filling its atmosphere with heat-trapping carbon dioxide. The result is a planet with 90 times the surface pressure of Earth’s, a temperature above 460 degrees Celsius (860 degrees Fahrenheit) and clouds made of sulfuric acid.

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Yet in its troposphere at an altitude of about 50 to 60 kilometers, Venus’s pressure and temperature are similar to those of Earth at sea level. The acid clouds and poisonous air would still be a problem, but in theory, it’s possible that humans could someday live in floating habitats high in the Cytherean skies—strange indeed.

Jupiter is the weirdest planet in the solar system. With a width of 11 Earths wide and a mass that is more than 300 times that of our planet, it’s a gas giant—a colossal bag of hydrogen and helium that turns into a bizarre liquid mix lower in its atmosphere and eventually becomes metallic even deeper down. As far as we can tell, Jupiter has a core of metal and rock, but it’s fuzzy and mushy—not at all like the obvious delineated layers we enjoy on our home world. And it has a powerful magnetic field that billows in the solar wind to stretch outward for hundreds of millions of kilometers, making this the largest continuous structure in the solar system after the sun’s heliosphere. If our eyes could see it, Jupiter’s magnetosphere would appear bigger than the full moon in the sky!

Mercury is the weirdest planet in our solar system. Scorched by the sun, it’s locked in a gravitational tug-of-war with our star that, over time, has forced the planet to spin three times for every two times it orbits the sun. Coupled with its elliptical orbit, this has strange effects; there are spots on the surface where, in the morning, you could watch the sun rise for a time, then set and then rise again, all near the same spot in the sky. And despite Mercury’s intense irradiation, there are deep, cold craters near its poles that never see sunlight and harbor water ice. It’s a planet of paradoxes.

Neptune is the weirdest planet in the solar system. The most distant major planet from the sun and the last stop before interstellar space, Neptune is only dimly illuminated by our star, receiving just 0.1 percent as much light as Earth does. It was discovered not by direct observation but with gravitational effect on Uranus, although it was spotted, unrecognized at the time, by Galileo centuries earlier. Its internal heat powers our solar system’s fastest winds, measured at an incredible 2,200 kilometers per hour—faster than the speed of sound. Don’t ever try to fly a kite at Neptune. It’ll tear your arms off.

Mars is the weirdest planet in the solar system. A tenth the mass of Earth, it nonetheless has the solar system’s tallest mountain and grandest canyon. It’s covered in fine-grained dust composed of various kinds of iron oxide: rust. The atmosphere is lousy with the stuff, tinting the air a butterscotch color—except near the sun in the sky, where light scattering creates a blue aura that is best visible at sunset. This makes it the opposite of Earth, with its blue skies and red sunsets.

Uranus is the weirdest planet in the solar system. Eons ago, some catastrophic event knocked the huge ice giant on its side, and it now orbits the sun with an axial tilt of 9