City-size 'cosmic butterfly' carved into Mars' surface contains traces of ancient water

A giant, city-size "butterfly" that was carved into the surface of Mars millions of years ago just got a new photo op thanks to European Space Agency (ESA) scientists. The beautiful Martian bug, which sports a pair of smooth rocky wings, is a stunning reminder of the Red Planet's violent and watery past, experts say.

The so-called butterfly is an asymmetrical impact crater, created when a hefty asteroid smashed into Mars in the distant past at an unusually low angle. It is located in the Idaeus Fossae region — an extremely uneven and previously volcanic region in Mars' northern lowlands — and is around 12.4 miles (20 kilometers) from east to west and 9.3 miles (15 km) from north to south. This makes the crater almost large enough to fit the island of Manhattan across its floor.

The latest images of the oval crater, which remains unnamed, were digitally created using topographical data collected by ESA's Mars Express orbiter, which has been scanning the Red Planet since 2003. The data was also used to create a short video that calls the crater a "cosmic butterfly" and shows what it would look like if you were to circle it in a helicopter (see below).

Unlike most other impact craters in the solar system, which are circular and eject material equally around their edges, the shallow angle of this incoming asteroid caused it to unevenly distribute the debris, creating the crater's wings.

"The collision caused two distinct lobes of material to be flung outwards to the crater's north and south, creating two outstretched 'wings' of raised ground," ESA representatives wrote in a statement describing the butterfly. This uneven impact also sculpted the crater's floor into an "irregular," walnut-like shape, they added.

Circling a martian butterfly - YouTube

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Craters like this are commonly known as butterflies because of their rounded shape and rocky wings, and they are exceedingly rare. However, this is not the first one to be spotted on Mars.

In 2006, around three years into the Mars Express orbiter's mission, the ESA spacecraft snapped a butterfly crater in the Hesperia Planum region in Mars' southern highlands. This crater is much more elongated than the Idaeus Fossae crater and arguably has a much more bug-like appearance. (Mars' southern highlands and northern lowlands lie on either side of a geographical anomaly that "splits" the planet near the equator.)

Studying these anomalous craters helps scientists better understand the angle and force of the impacts that formed them. It can also reveal clues about the hidden layers of Mars' surface and what conditions existed when the collisions occurred, according to Live Science's sister site Space.com.

In the latest case, the ESA team noticed that the wings of the butterfly are much smoother than its bobbly, walnut-like floor. This suggests that this material has been "fluidized," meaning that it has been mixed with water. This most likely happened when Martian ice buried beneath the crater was melted by the impact and released into the resulting explosion, ESA representatives wrote.

It is currently unclear exactly when the newly imaged insect crater was formed or how large and fast the meteor that birthed it was. However, fragments of the space rock could potentially remain within the crater.

Animals on Mars

This is not the first time that scientists have found animal impostors lurking on Mars' surface.

NASA's various Mars rovers have found multiple rocks that bear a striking similarity to living creatures, including a turtle poking its head out from its shell, which was snapped by Perseverance in August, and a coral-like structure photographed by the Curiosity rover in 2022.

From above, certain geological features also take on a surprising likeness to wildlife, such as the infamous "spiders on Mars," which are cracks that form when ice sublimates beneath the Martian surface and look like swarming arachnids.

In September 2024, the Mars Express orbiter also helped to reveal a hidden dog-shaped blob lurking beneath Mars' North Pole.

These animal associations are often made due to pareidolia — a psychological phenomenon in which the human mind perceives a familiar pattern, such as a face or image, in random objects or structures.