Scientists have delivered us another origin story today: about the formation of the planet Mars. New research from a Chicago scientist suggests the red planet developed in just a fraction of the time it took Earth, and effectively had its growth stunted.

Nicolas Dauphas says Mars is actually a planet embryo, in a state of arrested development. The University of Chicago professor says planets like Earth and Venus formed as several embryos collided and fused. Mars, though, grew rapidly from one original hunk of material.

“We think it took approximately 50 million years to grow a planet like Earth,” said Dapuhas. “And the result of our study shows that Mars grew in only two million years.”

The explanation might account for Mars’ small size – about one-tenth the mass of Earth.

Dauphas studied Martian meteorites and, by testing for certain isotopes, was able to essentially date when Mars’ core separated from its outer layers. His findings suggest that scientists can look to Mars to better understand the building blocks of Earth. The results are out today in the journal, Nature.

Meanwhile, NASA today announced that it has officially given up on the tough little Martian rover, Spirit. The high-tech dune-buggy-meets-Johnny-Five roamed Mars’s surface for six years, far longer than its designers ever imagined. In the process, it sent back stunning photos and plenty of data that scientists will be gnawing on for years.

NASA is still in touch with Spirit’s sibling, Opportunity. Meanwhile, they’re also toiling away on the next Mars rover, Curiosity, set to launch later this year. As Dave Chapelle put it, MARS, um, folks.