How do mountains form inside craters on the Moon?

Seen here is an animated model showing how mountains form at the center of large craters on the Moon.

A mountain rising in a large crater post-impact. Credit: Michael Packer

Craters on the Moon typically form when asteroids hit its surface. It is a process that was rampant in the early days of the solar system. In the last billion years or so, asteroids impacts have been rare but they do happen. Remember the dinosaurs?

The shape of a crater is determined by the intensity of the impact. Small craters up to ~20 km are typically smooth and bowl shaped. Beyond that size however, a mountain emerges!

Larger asteroids or ones with high velocities possess higher momentum. Upon impact with the lunar surface, a large or fast-moving asteroid explodes and the high momentum is transferred to the surface. The force imparted can be so high that in addition to the crater that’s formed, the surface in and around the impact point is compressed further and melts. After a certain level of compression, the melted material from the crust bounces back and forms a central mountain, as seen in the featured GIF. Here’s a more detailed one.

Emergence of a central mountain in a large crater post-impact. Credit: Nick Strobel

All lunar mountains in craters are formed by this process and near instantaneously so! Mountains on the Moon are thus a significant departure from those on Earth, which are mostly formed by tectonic activity, like the mighty Himalayas. On Moon Monday, we’ve covered many craters with central mountains.

  1. Central peak of Tycho crater
  2. Y-shaped mountains in King crater
  3. Arc-shaped mountain of Aristarchus
  4. Two central peaks of Copernicus

And we’ve covered ones with mountain rings too!

  1. The crowned crater of Schrödinger
  2. Arc-shaped mountain rings of Apollo
  3. Outstanding mountains rings of Orientale

Exploring central mountains of craters offer insights (literally and figuratively) into the lunar interior as well as crater formation. Many such central mountains are selected as potential landing sites under NASA’s Constellation Regions of Interest for future missions.

Can you imagine an entire mountain rising out of the Moon’s surface near-instantaneously? Lunar mountains are such a marvel! ❤

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