Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2022 March 9
The featured image shows a penny-sized rock on Mars
discovered by the Curiosity Rover in late February 2022.
The rock is unusual because it has several appendages that
make it appear a bit like a flower. 
Please see the explanation for more detailed information.

A Flower-Shaped Rock on Mars
Image Credit: NASA, JPL-Caltech, MSSS

Explanation: It is one of the more unusual rocks yet found on Mars. Smaller than a penny, the rock has several appendages that make it look, to some, like a flower. Although it would be a major discovery if the rock was truly a fossilized ancient Martian flower, there are less spectacular -- and currently preferred -- explanations for its unusual structure. One theory that has emerged is that the rock is a type of concretion created by minerals deposited by water in cracks or divisions in existing rock. These concretions can be compacted together, can be harder and denser than surrounding rock, and can remain even after the surrounding rock erodes away. The flower structure may also be caused by crystal clusters. The small rock, named Blackthorn Salt, has similarities to previously imaged Martian pebbles. The featured image was taken by the Curiosity rover on Mars in late February. Scientists will continue to study data and images taken of this -- and similar -- surprising Martian rocks.

Review: Last Year in Space Pictures
Tomorrow's picture: the toucan's star cluster

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