This is a very cool story. Scientists have discovered that Mars once had a mild temperature of 64 degrees Fahrenheit. They deduced the temperature from a rock found in Antarctica that had a wild ride starting four billion years ago. (Of course, the scientists again ignore the “creation science” account and misjudge the age of the rock by just short of four billion years).
Here is how it happened. The rock was formed just below the surface of Mars billions of years ago. Then, around 16 million years ago, a meteorite hit Mars — turning the rock into a meteorite itself and flying off the surface of the planet. It then landed on Earth 13,000 years ago in Antarctica. It was then found in 1984.
This year, a group of scientists sliced open meteorite ALH84001 and tested it at the California Institute of Technology. It yielded the first evidence of the surface temperature of Mars through an analysis of the carbonate minerals.
So to wrap this up, Mars was really cool; this little rock is really really old and these guys are really really really smart.