Possible recent lunar volcanism Options

[Bjorn Jonsson]

This is very interesting - and unexpected (at least to me):

http://lroc.sese.asu.edu/posts/818

Apparently there may be small features of volcanic origin on the Moon that are less than 100 million years old. The images are also very interesting - I would probably never have guessed that the image at the top was of lunar terrain.

[John Moore]

As to how Ina was made, and indeed other IMPs (Irregular Mare Patches - volcanic in nature) the most recent hypothesis suggests that the depression units are a left-over crust from a much larger lava lake
magma that developed deep down below within a dike/vent environment.

Essentially, the magmas produced a crust metres-thick composition in where numerous cracks formed during its cooling period, and that magmatic foamy deposits below (a mixture of magma with gases
created in the lava lake) squeezed through these cracks, producing the darker-looking, bulbous 'mounds' (as they are usually referred to) in the floor.

There are several other hypotheses as to IMP formation mechanisms. Surface features like craters, degradation and erosion effects, wall and mound slopes, regolith thickness, their surrounding mares etc.,
etc,. all have to be considered, too - each supporting the research posed in each hypothesis.

But the most important aspect about IMPs is the approximate age of them; where some hypotheses suggest that IMPs are young by millions of years, others suggest that they formed billions of years ago and
fit in with the generally-accepted theory that volcanism ended on the Moon round then. The age issue is very controversial today - because if they are young, then volcanism on the Moon ended later than
expected, and so thermal and magmatic models would have to be seriously revised.

A SmallSat concept mission, called IMPEL (Irregular Mare Patch Exploration Lander), could answer the question in the near future, particularly for Ina at which would be its intended target.

The various images out there of all IMPs proposed can be confusing - some views show them' flipped' or 'reversed' due to natural original images recorded by the Lunar Reconnaissance Orbiter (LRO) in its
orbit, some repeat odd-wise in a combination of both.

The forth-coming book, in early 2019, should set the record straight. All of the 70 so-far catalogued IMPs (with high-rez LROC images and lat/long coordinates) to date are included, as well as 40 additional
uncatalogued IMP features. LRO NAC numbers/references are also included with all, while a brief description on each and how to access them easily is included.

John Moore