An irregular mare patch also known as an IMP, is a smooth, rounded, slightly mounded area, generally about 500 meters wide, occurring in the

lunar maria The lunar maria (; singular: mare ) are large, dark, basaltic plains on Earth's Moon, formed by ancient asteroid impacts on the far side on the Moon that triggered volcanic activity on the opposite (near) side. They were dubbed , Latin for 'seas' ...

.Wood, Charles. "Strange Little IMPs." ''Sky and Telescope,'' February 2015 issue.

Discovery

Due to their small size, and corresponding difficulty of

observational astronomy Observational astronomy is a division of astronomy that is concerned with recording data about the observable universe, in contrast with theoretical astronomy, which is mainly concerned with calculating the measurable implications of physical m ...

from Earth, the first irregular mare patch discovered, Ina, was only found in 1971 after analysis of photographs taken by

Apollo 15 Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the United States' Apollo program and the fourth to Moon landing, land on the Moon. It was the first List of Apollo missions#Alphabetical mission types, J mission, with a ...

. More were discovered by the

Lunar Reconnaissance Orbiter The Lunar Reconnaissance Orbiter (LRO) is a NASA robotic spacecraft currently orbiting the Moon in an eccentric polar mapping orbit. Data collected by LRO have been described as essential for planning NASA's future human and robotic missions t ...

, which was launched in 2009 and found about 70 more.

Origin

The origin of the irregular mare patches is uncertain. Crater counts, which can give an indication of the age of an area by the number of craters upon it, indicate that these regions can be as young as a few tens of millions of years old. It has been hypothesized by the LRO team that they are small volcanic lava flows, due to their spectroscopic similarity to other lava flows. However, other analysts dispute this, noting that there are many separate patches, instead of one large patch. This would require numerous small-scale eruptions. There is also no indication of flowing, as there is in lava in other eruptions on the Moon. Even more important, the hypothesis of volcanic action is at odds with the current theory of the Moon's geology, which states that the moon should have cooled and solidified by about 1 billion years ago, precluding further geological action.

Geological implications

Understanding irregular mare patches may require new geological theories to be properly explained. According to the current scientific theories, the Moon's small size means that its mantle should have fully solidified by about 1 billion years ago, which is backed up by seismic data. This would prevent any further geological action by the Moon's interior. A recent (in geological terms) eruption would indicate that the Moon has cooled much more slowly than thought, possibly due to heat released from

radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...

of radioisotopes in the Moon.

Bibliography

* John Moore: ''Irregular Mare Patches on the Moon'' (2019).

References

{{Reflist Moon

Discovery

Origin

Geological implications

See also

Bibliography

References