Astronomers: Mercury has been shrinking for billions of years

Mercury, the closest planet to Earth and the other planets in our system, is very inhospitable: over the scorched surface there for 59 Earth days, the temperature remains at 430 degrees Celsius. However, while space tourism fans are justifiably wary of Mercury, scientists have a genuine interest in the planet.

In 1974, NASA’s Mariner-10 mission discovered peculiar slopes called “scarps” on Mercury. They were formed due to faults underneath and subsequent “thrusting” of plates. This is evidence of the planet’s compression as a result of thermal cooling.