The solar system is a place with its alien planets, mysterious moons and strange phenomena that are so out-of-this-world they elude explanation. Scientists have discovered ice-spewing volcanoes on Pluto, while Mars is home to a truly "grand" canyon the size of the United States. There may even be a giant, undiscovered planet lurking somewhere beyond Neptune. Read on to find out some of the strangest facts about planets, dwarf planets, comets and other incredible objects around the solar system.
Uranus is tilted on its side
Uranus appears to be a featureless blue ball upon first glance, but this gas giant of the outer solar system is pretty weird upon closer inspection. First, the planet rotates on its side for reasons scientists haven't quite figured out. The most likely explanation is that it underwent some sort of one or more titanic collisions in the ancient past. The tilt makes Uranus unique among the solar system planets.
Jupiter's moon Io has towering volcanic eruptions
The Jovian moon has hundreds of volcanoes and is considered the most active moon in the solar system, sending plumes up to 250 miles into its atmosphere. Some spacecraft have caught the moon erupting.
Venus has super-powerful winds
Venus is a hellish planet with a high-temperature, high-pressure environment on its surface. The planet has a bizarre environment. Scientists have found that its upper winds flow 50 times faster than the planet's rotation. It also found that the hurricane-force winds appeared to be getting stronger over time.
Spacecraft have visited every planet
We've been exploring space for more than 60 years, and have been lucky enough to get close-up pictures of dozens of celestial objects. Most notably, we've sent spacecraft to all of the planets in our solar system — Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune — as well as two dwarf planets, Pluto and Ceres.
There could be life in the solar system, somewhere
The life exists elsewhere in the solar system. But as we learn more about how "extreme" microbes live in underwater volcanic vents or in frozen environments, more possibilities open up for where they could live on other planets. These aren't the aliens people once feared lived on Mars, but microbial life in the solar system is a possibility.
There are mountains on Pluto
Pluto is a tiny world at the edge of the solar system, so at first it was thought that the dwarf planet would have a fairly uniform environment. That changed when NASA's New Horizons spacecraft flew by there in 2015, sending back pictures that altered our view of Pluto forever.
Pluto has a bizarre atmosphere
Pluto's observed atmosphere broke all the predictions. Scientists saw the haze extending as high as 1,000 miles (1,600 km), rising higher above the surface than the atmosphere on Earth. As data from New Horizons flowed in, scientists analyzed the haze and discovered some surprises there, too.
Rings are everywhere in the solar system
It took spacecraft and more powerful telescopes built in the last 50 years to reveal more. We now know that every planet in the outer solar system – Jupiter, Saturn, Uranus and Neptune – each have ring systems. That said rings are very different from planet to planet. Saturn's spectacular rings, which may have come from a broken-up moon, are not repeated anywhere else.
Jupiter's Great Red Spot is shrinking
Along with being the solar system's largest planet, Jupiter also hosts the solar system's largest storm. Known as the Great Red Spot (since it's big and ruddy-cooled), it's been observed in telescopes since the 1600s. Nobody knows exactly why the storm has been raging for centuries, but in recent decades another mystery emerged: the spots.
There may be a huge planet at the edge of the solar system
There could be a giant planet lurking far beyond Neptune. Several teams are now on the search for this theoretical "Planet Nine," which could take decades to find (if it's actually out there.)