It’s time to showcase lunar swirls again! The previous Image of the Week to focus on lunar swirls was in July 2010 (see link below) and since then more work has been done on what they actually are.
Lunar swirls are bright areas on the lunar surface that are associated with magnetic anomalies in the Moon’s crust. It is thought that these weak magnetic fields prevent the solar wind from changing the surface which is why it remains brighter than the surrounding area which slowly darkens as the solar wind modifies it.
We appear to know why lunar swirls form (due to the magnetic anomalies) but we still don’t know why the magnetic anomalies are where they are and why and how they formed.
The LROC article below, The Swirls of Mare Ingenii, is well worth a read and has some stunning images of swirls.
Reiner Gamma swirl (Latitude: 7.25 Longitude: -60.62)
Quote: Lunar swirls are among the most beautiful and bizarre features on the Moon. Seen as bright, sinuous regions, swirls are associated with weak magnetic anomalies in the Moon’s crust. Images from LROC, and the topographic information extracted from those images, have shown that swirls have no topography associated with them; they are not higher or lower than their surroundings. Instead, it is as if someone has taken a brush and laid down a beautiful swath of bright paint.
Quote: Scientists from RAL Space at the Rutherford Appleton Laboratory have solved a lunar mystery and their results might lead the way to determining if the same mechanism could be artificially manipulated to create safe havens for future space explorers. Their work focussed on the origin of the enigmatic “lunar swirls” – swirling patches of relatively pale lunar soil, some measuring several tens of km across, which have been an unresolved mystery – until now.
Linné crater is a young, well preserved impact crater on the western edge of Mare Serenitatis, at coordinates: latitude = 27.7, longitude = 11.8. It is 2.2 km in diameter and bowl-shaped and is often cited as a good example of a fresh impact crater. Its actual age is unknown but thought to be less than 10 million years.
It has been used to investigate how cratering occurs in mare basalts and the report from the 42nd Lunar and Planetary Science Conference (2011) has a very good description of the crater and compares it to the terrestrial Barringer Crater (aka Meteor Crater). The report can be found here: Linne: Simple Lunar Mare Crater Geometry from LRO Observations
There is some controversy about Linné crater to do with ‘transient lunar phenomena’ (TLP) maybe caused by outgassing. In the nineteenth century some astronomers believed that they had seen changes around the crater, in some cases they said that the crater had vanished leaving only a mound behind. This is discussed here: The Linné Crater Controversy
[NASA/GSFC/Arizona State University]
Colour coded shaded relief map of Linné crater created from an LROC NAC stereo topographic model. The colours represent elevations; cool colours are lowest and hot colours highest.
The following site contains a movie of a “fly around” Linné crater:
The ‘Lake of Death’ (Lacus Mortis) lies in the northeastern part of the Moon, north of Mare Serenitatis, and is either an ancient crater or a basin, which has been flooded by lava. It is about 150 km in diameter with the crater Burg, which was formed less than a million years ago, situated approximately in the centre. Lacus Mortis was named by selenographer Giovanni Riccioli in 1651 but he gave no reason for its strange name.
Lacus Mortis also contains one of the few “true” faults found on the Moon and you can see it (marked with an orange arrow) in the image below starting at the southern boundary of Lacus Mortis and going north before finally turning into a rille. (See the first link under Useful Links for more images of the fault).
The western half of Lacus Mortis also contains several rilles, the main one of which is Rimae Burg which is over a 100 km in length and is a graben. Where this rille crosses the boundary between Lacus Mortis and the highlands in the southwest, there are some volcanic cones – see link #4 under Useful Links for more information.
A larger image containing feature names will be found here: LROC Context Image
Burg crater, within Lacus Mortis, is worth exploring as it has many boulder tracks and some nice landslide textures on the western crater wall. See links #2 and #3 under Useful Links for more information.
Boulder tracks within Burg crater
Landslide textures from inner wall of Burg crater, western side.
A true fault in Lacus Mortis: Lacus Mortis Fault
Boulder tracks within Burg crater: A Gathering in Lacus Mortis
Description of Burg crater: Not your average complex crater
Volcanic domes: Volcanoes in the Lake of Death
A mystery! Tidbits of Strangeness
The Image of the Week for 20th February 2012 featured exploding boulders, discovered by Dr Anthony Cook, in Schiller crater which is located in the southwestern region of the Moon, south of Oceanus Procellarum at coordinates 51.8 S / 40.0 W. This crater is interesting in its own right apart from the exploding boulders!
Schiller crater is one of the most uniquely shaped craters on the Moon and its formation is still a bit of a mystery. It is elongated as if it had been stretched lengthwise at some point but was probably created by a grazing (oblique) impact or is a secondary impact crater. At least one article claims that it was created by a multiple impact, i.e. the impacting object broke up just before hitting the Moon (see Formation of Irregular Craters on the Moon below).
The crater is approximately 180 km in length and 70 km wide.
The image below is an LROC WAC Global 100 meter mosaic draped over the laser altimetry (LOLA) digital elevation model as seen from an imaginary point 65 kilometers over the elongated crater’s southeast.
Credit: NASA/GFSC/Arizona State University
An interesting article about boulders and boulder tracks around the central peak complex of Schiller crater. Some worthwhile images in the article.
LROC: A Recent Journey
The Boulder Tracks thread is one of the most popular within the Moon Zoo forum and we have some amazing tracks posted there.
Boulder tracks are important to the Moon Zoo project – the following quote is from one of the Moon Zoo team members:
One of the main reasons we are asking Moon Zoo users to search for scars left behind by tumbling boulders is to help support future lunar exploration initiatives. Boulders that have rolled down hillsides from crater walls, or massifs like the Apollo 17 landing site, provide samples of geologic units that may be high up a hillside and thus difficult to access otherwise by a rover or a manned crew vehicle. If mission planning can include traverses to boulders that have rolled down hills, and we can track these boulders back up to the part of hillside from where they have originated, it provides a neat sampling strategy to accessing more geological units than would have been possible otherwise… Thus we hope to use Moon Zoo user data to produce a map of known boulder tracks (and terminal boulders) across the Moon. – Katie Joy
Recently ElisabethB (Els) posted the tracks shown below. Quite an amazing variety of track sizes and shapes! The track on the bottom appears to have mounds inside the track caused by the shape of the boulder that created the track.
Also, some of the tracks have craters overlapping them which may have been caused by the same impact. The original impact would have sent boulders bouncing and rolling along the regolith but would also have sent boulders upwards and they would have eventually fallen back and created craters.
The area where these tracks are found is Montes Alpes / Vallis Alpes.
Sun Angle: -62.71°
Scale: 0.51 meters / pixel
Zoom Level: 3