MSL Curiosity is busy studying Mars. The high-tech rover is currently investigating a sulfate-containing blob on Mount Sharp, the central peak of Mars Gale Crater. Serendipity put a metallic meteorite in its path. The meteorite is mostly made of nickel and iron and has a name: Cocoa. (Chocolate comes from cocoa.) Cocoa is not very large; only 30 cm (1 ft) in diameter.

Curiosity found several meteorites after landing in Gale Crater in August 2012.

Cocoa visually stands out from the environment. Although the surface of Mars is red from the oxides, the meteorite is dark gray and metallic. It is also smooth and rounded, clear signs that it has passed through the atmosphere.

The image consists of six separate images taken by the rover’s Mastcam camera. Curiosity, images of task 3,724. Drawn on January 27, 2023, which is Mars day or sol. Colors in the image have been corrected to match the lighting conditions the human eye sees on Earth. Grooves and pits are called rhegmaglypts. They are especially interesting in iron meteorites. They were formed when cocoa circulated through the atmosphere.

Although the Martian atmosphere is much thinner than Earth’s, it still creates enough friction to heat the meteorite’s surface. Regmaglypts are likely created by eddies of hot gas that melt the rock as it travels through the atmosphere. The meteorite may be on the surface of Mars for a long time, but no one knows for sure.

This isn’t the first meteorite found on Mars. In 2016, MSL Curiosity found another golf ball-sized metallic meteorite called “Egg Rock.” He tested it with a ChemCam device to determine its composition.

A grid of five small white dots shows where the device’s laser hit the stone.

Iron-nickel meteorites are the rarest type of meteorite, accounting for about six percent of observed falls. However, they are over-represented in collections due to their brilliant visual appearance. This is because they are more likely to survive as they pass through the atmosphere and are more weather resistant, even on Mars.

Most iron-nickel meteorites come from the cores of destroyed planetesimals that formed in the early solar system. These objects were large enough to distinguish them when melted. They formed a dense core of iron and nickel, similar to Earth.

But life as a minor planet was risky and many crashed into asteroids. This is the possible story of cocoa. This is what makes meteorites, especially metallic ones, so scientifically interesting. They can stretch back billions of years from the beginning of the solar system.

Meteorites like cocoa were the first source of iron for humanity on Earth. Long before smelting, humans collected as many of these meteorites as they could and made knives and other tools from them. King Tut was buried with a dagger made of meteoric iron, while the Inuit in the Arctic and Greenland also used meteoric iron.

A particularly large iron meteorite called the Cape York meteorite has visited many times. They struck pieces of iron to make harpoon heads and started their own Iron Age, knowing nothing about smelting. They even traded iron with other human groups.

However, only our research robots will be able to see Cocoa.

Cocoa is an interesting oddity for MSL Curiosity. Curiosity’s mission is to explore features such as Gale Crater, Mount Sharp, and the Sulphur-bearing Block. The block is rich in salt minerals that form in the presence of water. By exploring this region, Curiosity sheds light on the ancient history of Mars and how it dried up and turned into the parched land it is today.