Buzz
We've sent astronauts to the moon and dispatched car-sized rovers to explore Mars. We've also cataloged almost 1,800 exoplanets around distant stars. It’s easy to think we’ve got a solid grasp of the cosmos. But then you stumble upon the strange giant hexagon on Saturn, and suddenly, it's clear we still have so much more to learn about our cosmic neighbors. These mysteries remind us that we'll need even more robots to uncover the truth.
10. The Venusian Vortex
A massive vortex near Venus's south pole behaves like a storm, but without rain or lightning. It stretches across 1,800 kilometers (1,200 miles), reaches a height of 18 kilometers (12 miles), and sits 41 kilometers (26 miles) above the surface of the planet. Initially thought to be oval in shape, scientists discovered in 2011 that it changes form regularly. At times, it takes the shape of an “S” or an “8,” but often it’s just an irregular blob. It orbits about three degrees off the south pole every 5 to 10 days.
In 2013, scientists realized it isn't a single vortex, but actually two separate vortices with distinct centers of rotation at different altitudes. These vortices sometimes break apart and come together, but they rarely align. Researchers expected them to behave as a unified feature, yet they remain uncertain about why they don’t. This might be related to Venus's atmosphere rotating 60 times faster than the planet itself, but the exact relationship is still unclear.
9. The Intriguing Iapetus
Iapetus, Saturn’s third-largest moon, has intrigued astronomers since Giovanni Cassini first observed it in 1671. Cassini noticed that the moon’s leading face, the one in front of its orbit, was darker than the trailing hemisphere. In fact, the back is 10 times brighter.
For 336 years, this peculiar phenomenon baffled scientists until we sent a probe past Saturn—appropriately named after Cassini. Researchers discovered that the moon initially gathered dust as it moved, which darkened the front. This increased sunlight absorption caused the ice there to melt, further darkening it, and the cycle continued.
While the Cassini probe solved one mystery, it uncovered another. An 18-kilometer-high (12 mi) ridge encircles most of Iapetus's equator—over twice the height of Everest on a moon just one-ninth the size of Earth. One theory suggests Iapetus had a ring that collapsed onto the surface, forming the ridge. Another theory posits that a 1,000-kilometer-wide (650 mi) asteroid impacted Iapetus, causing the moon’s rotation to slow and resulting in stress that flattened the poles and created a central bulge.
Iapetus not only provides its own enigmas but might also offer clues to solving those on other planets. A sturzstrom is a type of landslide found on Earth and Mars that travels about 15 times farther than most landslides, and the cause remains unknown. One theory suggests that sound waves cause rock particles to behave like a fluid. These landslides are incredibly common on Iapetus, so studying its surface may bring us closer to understanding the origin of sturzstroms.
8. The Spider on Mercury
When NASA’s MESSENGER probe passed by Mercury in January 2011, it captured a photograph of an impact crater unlike any other in the solar system. Dubbed “the spider,” the crater features around 50 troughs radiating outward from the basin in all directions. A scientist from the lab that helped develop the probe called it “a real mystery” and suggested volcanic activity could be responsible. The structure was later officially named “Pantheon Fossae,” inspired by the Pantheon dome in Rome, with Fossae meaning “trenches” in Latin. The central crater was named Apollodorus, after the chief architect of the Pantheon.
High-resolution images indicate that the 41-kilometer-wide (27 mi) crater may not be connected to the trenches at all, as it’s slightly offset. A meteor could have impacted near the center after the pattern had already formed.
7. Miranda: A Chaotic Moon
Miranda, Uranus’s fifth-largest moon, is the most bizarrely shaped moon in the solar system. NASA even describes it as “like Frankenstein’s monster” because its pieces seem mismatched. Its odd patchiness is easily seen in images taken by Voyager 2, with sharply defined boundaries separating lightly cratered regions from heavily bombarded ones. The deepest ridges between these areas are 12 times deeper than the Grand Canyon.
This strange appearance is unlike anything else in the solar system, and scientists are unsure about its origin. One hypothesis suggests that the moon was struck with such force that it broke apart, only to be pulled back together by gravity in a disorganized fashion. Another possibility is that the smoother regions, known as coronae, were bombarded by meteorites that melted the ice, creating slush that flowed across the surface before refreezing.
6. The Enigmatic Spots on Uranus
In 2006, the Hubble and Keck telescopes spotted a dark spot on Uranus. Similar spots had been observed on Neptune, likely caused by atmospheric eddies. However, scientists are uncertain about the cause of the darkness. It could be a gap in the clouds, revealing deeper layers of the planet, or perhaps something dark has risen from below or formed at higher altitudes.
In 2011, astronomers discovered the opposite—a massive white spot, 10 times brighter than the surrounding atmosphere. It appeared to span hundreds of miles and might have been a giant methane storm. In response, Hubble was quickly pointed at the planet, revealing that the bright spot was accompanied by a dark spot right next to it.
Unfortunately, we still can't explain the darkness we're witnessing. To answer this question, it seems we will need to send a probe to Uranus.
5. Plumes on Ceres
Ceres is the largest asteroid as well as the biggest dwarf planet in our solar system. Previously, we discussed that it might contain more water than all the fresh water on Earth. Since then, scientists have found that Ceres is ejecting some of this water into space. The European Space Agency's Herschel space telescope detected vapor plumes, but the mystery remains as to what is causing them.
There are two leading theories. Since the vapor comes from the darker regions of the planet, these areas could be absorbing sunlight. When light heats the ice in a low-pressure environment, the water bypasses the liquid phase and turns directly into gas. Alternatively, volcanic activity might be happening beneath the surface of the dwarf planet.
We may have an answer by 2015, as NASA’s Dawn probe is currently en route.
4. Mercury Is Bulging
The spider is not the only striking mystery revealed on Mercury by the MESSENGER probe. In fact, many of our earlier theories about Mercury’s formation have been replaced by new questions.
Something inside the planet seems to have caused previously sloped surfaces to level out, while flat areas have turned into slopes. The floor of Mercury’s largest crater has risen above its rim in some locations. Scientists are unsure why this is happening or whether more changes are forthcoming. It’s believed that Mercury’s mantle is too thin for the processes responsible for topographic shifts on other planets. Understanding what’s happening here could reshape our knowledge of rocky planets.
Mercury has a strange structure. Its solid core makes up more than half of its width, which is five times larger than Earth’s proportion. The Sun might have stripped away the planet’s outer layers, or perhaps a giant collision caused the loss. However, volatile elements that should have vanished during either of these events remain in similar proportions to those found on Earth and Venus, throwing doubt on both explanations.
3. Chaos Terrain
Some landscapes in the solar system are remarkably chaotic. Mars’s Aureum Chaos features winding ridges and valleys, with mesas and hills placed at random. Iani Chaos is another Martian region characterized by its disordered ridges. There are even examples without the word “Chaos” in their name.
Scientists are still puzzled about the formation of these areas. It’s possible that the region beneath Mars’s chaos terrain once contained water or magma, which flowed away and caused the surface to collapse and fracture. However, not all chaos terrain areas fit this theory, and there’s ongoing debate over whether wind or water played a role in their creation.
Mercury’s chaotic terrain likely has a different explanation. The Caloris Basin, the largest impact crater on the planet at around 1,500 kilometers (930 mi) across, was formed by a massive impact. This event sent seismic waves through Mercury, and the opposite side of the planet is covered by a distorted, chaotic landscape as a result of these waves.
Jupiter’s moon Europa also features jagged, disrupted landscapes. One particularly stunning region, named Conamara Chaos, highlights the chaotic nature of this terrain. These regions are believed to have formed when warm water currents melted Europa's icy crust, creating vast subsurface lakes. The ice above fractures, and the resulting sections float and rotate before refreezing, leaving behind a chaotic terrain.
2. Io’s Out-Of-Place Volcanoes
Jupiter’s gravity pulls the moon Io in one direction, while the larger moons exert their own gravitational forces in different ways. This causes tidal forces that stretch and heat up Io, giving rise to its dramatic volcanic activity. Io is the most volcanically active body in the solar system, with some eruptions sending lava 375 kilometers (250 mi) above its surface. However, these volcanoes occur in locations that don’t fit any of the existing models of tidal heating.
The volcanoes on Io were expected to emerge from areas with soft rock, which would be more susceptible to deformation and heating. However, they appeared 30 to 60 degrees east of the anticipated spots. This discrepancy suggests that either our models are flawed or something else is at play. It’s possible that Io rotates faster than previously thought, or that magma is being transported across vast distances within the moon's interior.
1. The Ashen Light Of Venus
The mysterious Ashen Light, observed on the dusk side of Venus, was first recorded in 1643 and has caught the attention of some of the greatest minds in astronomy. Between 1954 and 1962, it was spotted at least 129 times. Despite so many reports, some argue that the Ashen Light might just be an observational artifact, while others are convinced it’s a genuine phenomenon.
In the 19th century, astronomer Franz von Paula Gruithuisen speculated that the Ashen Light was caused by Venusians setting fire to forests, either to clear land for farming or to celebrate their new planetary emperor. Modern theories, however, are more scientific. One suggests that sunlight breaks down carbon monoxide on the planet's day side, and the gas then recombines on the night side, carried by strong winds. Other theories point to powerful lightning storms or possible auroras.
+Lines All Over Europa
Europa’s surface is a strange sight, extending far beyond its chaotic terrain. In 1999, researchers uncovered the cause behind the moon’s cycloidal ridges—enormous arcs that stretch for hundreds of miles. These ridges result from the tidal forces of the moon’s subsurface ocean pressing against the icy shell. As Europa orbits Jupiter, the focus of this pressure moves in an arc, with each orbit producing one of these sweeping curves.
In addition to the ridges, the tides create long, straight lines across Europa’s surface, known as lineaments. These lines crisscross the moon in various directions, which is puzzling since the same side of Europa always faces Jupiter. One theory suggests the icy shell rotates at a faster rate than the moon's orbit, but newer evidence points to a potential tilt in Europa’s rotational axis as the cause. It’s also possible that a combination of these factors is at work.
