Science is great. We think we have a problem solved, all the loose ends tied up, and then up pops a new discovery. Some see this as evidence of science’s fragility. Of course those people don’t understand the scientific method. In science, nothing is sacred, nothing is sacrosanct, everything is open to new data.
The latest episode to remind us of the power of the scientific method involves the Man on the Moon – the dark region known as Procellarum that is easily visible from Earth. As one of many Lunar Maria, we automatically thought it formed the same way as the other Maria – a late giant impact broke through the surface and cause lava to flow up, which then cooled as the dark material we see. But new data obtained by NASA’s GRAIL mission reveals that the Procellarum region likely arose not from a massive asteroid strike, but from a large plume of magma deep within the moon’s interior.
Scientists have created a map of the Procellarum, and found that its border is not circular, but polygonal, composed of sharp angles. These could not have been created by a massive asteroid. Instead, it is more likely that these were produced by giant tension cracks in the moon’s crust as it cooled around an upwelling plume of hot material from the deep interior. As cracks occurred, they formed a “plumbing system” in the moon’s crust through which magma could meander to the surface.
So it turns out that we were right about the lava flow part, but at least for this Maria, we were probably wrong about how the lava came up.