6 min read

10 Things: Greatest Hits – Craters We Love

Roundish, reddish moon with massive crater on one end.
With a diameter of 5.6 miles (9 kilometers), Stickney Crater is the most prominent feature on Mars' moon Phobos.
NASA/JPL-Caltech/University of Arizona

Our solar system was built on impacts: Some big, some small – some fast, some slow. Here’s a short list through some of the more intriguing impacts across our solar system.

Color-enhanced view of Caloris Basin on Mercury
Enhanced-color view of Mercury's Caloris Basin.
NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

1. Mercury: A Basin Bigger Than Texas

Mercury does not have a thick atmosphere to protect it from space debris. The small planet is riddled with craters, but none as spectacular as the Caloris Basin. “Basin” is what geologists call craters larger than about 186 miles (300 kilometers) in diameter. Caloris is about 950 miles (1,525 kilometers) across and is ringed by mile-high mountains.

For scale, the state of Texas is 773 miles (1,244 kilometers) wide from east to west.

Large crater on Venus
Margaret Mead Crater on Venus.

2. Venus: Tough on Space Rocks

Venus’ ultra-thick atmosphere finishes off most meteors before they reach the surface. The planet’s volcanic history has erased many of its craters, but like almost any place with solid ground in our solar system, there are still impact scars to be found. Most of what we know of Venus’ craters comes from radar images provided by orbiting spacecraft, such as NASA’s Magellan.

Mead Crater is the largest known impact site on Venus. It is about 170 miles (275 kilometers) in diameter. The relatively-flat, brighter inner floor of the crater indicates it was filled with impact melt and/or lava.

Just 114 miles from the newly-found Hiawatha impact crater under the ice of northwest Greenland, lies a possible second impact crater. The 22-mile wide feature would be the second crater found under an ice sheet, and if confirmed, would be the 22nd-largest crater on Earth.
NASA's Goddard Space Flight Center/Jefferson Beck

3. Earth: Still Craters After All These Years

Evidence of really big impacts – such as Arizona’s Meteor Crater – is harder to find on Earth. The impact history of our home world has largely been erased by weather and water or buried under lava, rock, or ice. Nonetheless, we still find new giant craters occasionally.

That followed the finding, announced in November 2018, of a 19-mile-wide crater beneath Hiawatha Glacier – the first meteorite impact crater ever discovered under Earth’s ice sheets. Though these impact sites in northwest Greenland are only 114 miles apart, at present they do not appear to have formed at the same time.

If the second crater, which has a width of over 22 miles, is ultimately confirmed as the result of a meteorite impact, it will be the 22nd largest impact crater found on Earth.

"We’ve surveyed the Earth in many different ways, from land, air, and space – it’s exciting that discoveries like these are still possible," said Joe MacGregor, a glaciologist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who participated in both findings.

Mountain in the middle of Moon crater
Tycho Crater's central peak on the Moon.
NASA Goddard/Arizona State University

4. Moon: Our Cratered Companion

Want to imagine what Earth might look like without its protective atmosphere, weather, water, and other crater-erasing features?

Look up at the Moon.

Graphic with location of Tycho in lower left quadrant of the Moon.
Tycho Crater on the Moon.
NASA/Goddard/Arizona State University

The Moon’s pockmarked face offers what may be humanity’s most familiar view of impact craters.

One of the easiest to spot is Tycho, the tight circle and bright, radiating splat are easy slightly off center on the lower-left side of the full moon.

Closer views of the 53-mile (85-kilometer)-wide crater from orbiting spacecraft reveal a beautiful central peak, topped with an intriguing boulder that would fill about half of a typical city block.

Fresh impact crater on Mars.
A new impact on Mars as seen from orbit.
NASA/JPL-Caltech/University of Arizona

5. Mars: Still Taking Hits

Mars has just enough atmosphere to ensure nail-biting spacecraft landings, but not enough to prevent regular hits from falling space rocks. This dark splat on the Martian south pole formed between July and September 2018. The two-toned blast pattern tells a geologic story. The larger, lighter-colored blast pattern could be the result of scouring by winds from the impact shockwave on ice. The darker-colored inner blast pattern is because the impactor penetrated the thin ice layer, blasting the dark sand underneath in all directions.

Crater with bright white area in center.
Simulated view of Occator Crater revealing the crater's unique features.

6. Ceres: What Lies Beneath

The bright spots in Ceres’ Occator crater intrigued the world from the moment the approaching Dawn spacecraft first photographed it in 2015. Closer inspection from orbit revealed the spots to be the most visible example of hundreds of bright, salty deposits that decorate the dwarf planet like a smattering of diamonds. The science behind these bright spots is even more compelling: they are mainly sodium carbonate and ammonium chloride that somehow made their way to the surface in a slushy brine from within or below the crust. Thanks to Dawn, scientists have a better sense of how these reflective areas formed and changed over time – processes indicative of an active, evolving world.

7. Comet Tempel 1: We Did It!

Scientists have long known we can learn a lot from impact craters – so, in 2005, they made one themselves and watched it happen.

On July 4, 2005, NASA’s Deep Impact spacecraft trained its instruments on an 816-pound (370-kilogram) copper impactor as it smashed into comet Tempel 1.

One of the more surprising findings: The comet has a loose, “fluffy” structure, held together by gravity, and contains a surprising amount of organic compounds that are part of the basic building blocks of life.

Moon with giant impact crater on its side.
Herschel Crater on Saturn's moon Mimas.
NASA/JPL-Caltech/Space Science Institute

8. Mimas: May the 4th Be With You

Few "Star Wars fans – us included – can resist Obi-Wan Kenobi's memorable line “That’s no moon…” when images of Saturn’s moon Mimas pop up on a screen. Despite its Death Star-like appearance, Mimas is most definitely a moon – our Cassini spacecraft checked – and the super laser-looking depression is simply an 81-mile (130-kilometer) wide crater named for the moon’s discoverer, William Herschel.

Bright impact crater on Europa
Pwyll Crater on Europa.
NASA/JPL/University of Arizona

9. Europa: Say What?

The Welsh name of this crater on Jupiter’s ocean moon Europa looks like a tongue-twister, but it is perhaps easiest pronounced as “pool.” Pwyll is thought to be one of the youngest features we know of on Europa. The bright splat from the impact extends more than 600 miles (about 1,000 kilometers) around the crater, a fresh blanket over rugged, older terrain. “Fresh,” or young, is a relative term in geology; the crater and its rays are likely millions of years old.

Crater-riddled moon.
Saturn's moon Hyperion.
NASA/JPL-Caltech/Space Science Institute

10. Show Us Your Greatest Hits

Got a passion for Stickney, the dominant bowl-shaped crater on one end of Mars’ moon Phobos? Or a fondness for the sponge-like abundance of impacts on Saturn’s battered moon Hyperion (pictured)? There are countless craters to choose from. Share your favorites with us on Twitter, Instagram and Facebook.