Impact craters occur on every solid body in the Solar System. Indeed, it is the dominant process affecting surfaces on most extraterrestrial bodies today.
On Earth, however, such craters are often lost to time due to active geological processes, but elsewhere in the Solar System there are some truly awe-inspiring examples of impact craters preserved for all to see.
Here, we handpick the highlights of what the Solar System has to offer.
1. Basin of the South Pole of Aitken, the Moon
Our first crater is big: the largest, deepest, and oldest impact crater on the Moon. It has a diameter of 2,500 km, a depth of between 6.2 and 8.2 km and was formed about 4.2 billion years ago. As the name suggests, it is located at the south pole on the far side of the Moon, although the crater rim can be seen from Earth as a dark mountain range, just at the border between the light and dark sides of the moon.
It is a favorite site for lunar scientists to visit and learn about the geology of our moons. The depth excavated by the crater is nearly as deep as the deepest oceanic trenches on Earth. It offers us a unique insight into the interior of the lunar crust, with 4.2 billion years of history exposed.
In 2019, a Chinese space agency rover, Chang’e 4, landed in the basin and conducted the first scientific experiments there. One of the most interesting of these was the Lunar Micro Ecosystem, a collection of insect seeds and eggs designed to see if life could thrive in a tiny biosphere on the surface.
2. Unnamed crater (S1094b), Mars
There are many famous craters on Mars, from the homes of Mars rovers (Gale Crater for Curiosity or Jezero for Perseverance) to speculated origin regions of Mars meteorites (Tooting or Mojave). But one of the newest craters on the red planet is actually quite dramatic.
While rovers on Mars claim all the glory for exploring the Martian surface, satellites orbiting Mars have been making discoveries of their own for decades. NASA’s Mars Reconnaissance Orbiter (MRO) was launched in 2005 but is still operational, and its 16+ years of images of the surface of Mars allow us to make year-over-year comparisons, highlighting the differences between the data sets.
On Christmas Eve 2021, NASA’s InSight mission detected a large Marsquake on the red planet, which MRO data later helped identify as a new impact on the other side of Mars.
The vibrant, fresh impact ejecta (covered in material thrown off by the impact) can be clearly seen from space using data from the orbiter’s onboard contextual camera, and thanks to InSight we even know what it sounded like.
3. Enki Catena, Ganymede
Enki Catena is a chain crater on Ganymede, one of Jupiter’s Galilean moons. At last count, Jupiter has more than 90 moons, a mini planetary system in its own right.
Jupiter’s gravity creates tidal forces that shape the moons and give us some of the most interesting geological features we’ve ever found, from the volcanoes of Io to the subterranean ocean of Europa. There are also strings of craters found on two of the moons, Callisto and Ganymede.
These chains of craters were first spotted when the Voyager 1 spacecraft gave us some of the first images of these moons’ surfaces in 1979. They were thought to be potentially collapsed lava tubes, features that have been observed on Mars and on the moon.
However, their origin remained in dispute until Comet Shoemaker-Levy 9 was observed crashing into Jupiter. The comet was seen breaking into multiple pieces and this gave insight into how these chains might form as Jupiter’s gravity separates the objects into many pieces that all collide together.
Enki Catena is a chain of 13 craters spanning from an area of dark to bright terrain on Ganymede. It is 162 km long and about 10 km wide.
The European Space Agency’s Juice mission will visit the Jupiter system in the 2030s and allow us to see the surfaces in greater detail than ever before. We might even find more of these crater chains.
Read more: The long-awaited JUICE mission to Jupiter launches today. Here’s what he might find out
4. Occator crater, Ceres
Ceres is the largest body in the main asteroid belt between Mars and Jupiter. It is large and round enough to be considered a dwarf planet (along with Pluto and three less famous examples, Eris, Makemake and Haumea).
Occator crater on Ceres is impressive because it contains a bright spot at its center that has been observed both from space and from Earth at Mauna Kea Observatory in Hawaii.
NASA’s Dawn mission entered an orbit around Ceres in 2015 and imaged the bright spot in Occator crater known as Spot 5. It’s a three-kilometer-wide dome covered in luminous salts on the crater floor, possibly due to the hydrothermal activity.
Occator crater itself is 92 km in diameter and 3 km deep. The simulations indicate that the impactor (the space rock that created the crater) was about 5 km in diameter, impacting Ceres some 2025 million years ago.
5. Aurelia, Venus
Venus is sometimes called Earth’s twin. It’s when it comes to size, but the surface images we have of Venus show that the planets have very different characteristics.
The best images of this type were taken in the 1990s by NASA’s Magellan spacecraft. Venus has a thick, cloudy atmosphere, and visible light cameras cannot see through the surface. Magellan was equipped with radar that can see the surface but the images can be more difficult to interpret.
In radar, dark terrain is very smooth and light terrain is very rough. This makes impact craters stand out very well in radar images. The ejecta are very rough, especially against the surrounding volcanic plains, so they appear bright in images.
This is Aurelia, a 32 km impact crater on Venus.
You can see it silhouetted against the gray plains that surround it. The black soil on the edges of the bright white ejecta are fluid streams of rock that melted away when the impact hit.
Speaking of volcanoes on Venus, recently a group from the University of Alaska Fairbanks used this Magellanic data to find the first active volcano on Venus
NASA has three missions to Venus in development over the next 10 years, so hopefully we’ll soon know a lot more about our enigmatic twin.
Read more: These 5 spectacular impact craters on Earth highlight our planet’s wild history
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