Archive by Author | geoffroynon

Stuart’s Event

This week we have a mystery from the 1950s which we may be able to help resolve.

An amateur astronomer from Oklahoma, Dr. Leon Stuart, photographed a bright flare on the surface of the Moon while tinkering with his new camera in November 1953. The flare or flash was close to the Moon’s terminator and near the centre of the Moon’s face (see following image) and lasted for approximately eight seconds. Dr. Stuart published his photograph and description of the sighting in The Strolling Astronomer newsletter in 1956. He remained convinced until the end of his life that he had seem an asteroid impact the Moon’s surface but most astronomers were skeptical and said that the flash was either a meteor burning up in the Earth’s atmosphere which just happened to appear as if it was an impact on the Moon, or it was a problem with the film in the camera.
Dr. Stuart logged the event as follows:

Made by Dr. Leon Stuart, Nov. 15, 1953 at 01:00 UT. Lasted 8 to 10 sec. Also observed visually. Star images rather steady, no extraneous lights. Exposure: 1/2 sec. on E.K. 103aF3 plate. 8 inch f/8 reflector.
Position on Lunar surface is about 10 miles S.E. of Pallas. (-0.5; +.08).

Photo from Dr. Leon Stuart

Within astronomy circles Dr. Stuart’s impact was known as Stuart’s Event and was mostly ignored until recently (2002) when two scientists took an interest in this 50-year old mystery. Dr. Bonnie J. Buratti, a scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California and Lane Johnson of Pomona College, Claremont, California, researched the event and their findings included some very persuasive evidence which indicated that Stuart’s photo was indeed real and is of immense historical value.

Stuart’s remarkable photograph of the collision gave us an excellent starting point in our search, we were able to estimate the energy produced by the collision. But we calculated that any crater resulting from the collision would have been too small to be seen by even the best Earth-based telescopes, so we looked elsewhere for proof. Using Stuart’s photograph of the lunar flash, we estimated the object that hit the Moon was approximately 20 meters (65.6 feet) across, and the resulting crater would be in the range of one to two kilometers (.62 to 1.24 miles) across. We were looking for fresh craters with a non-eroded appearance. [Dr. Bonnie Buratti]

The two scientists decided to search for the crater using images taken from spacecraft orbiting the Moon. They had no luck with images from the Lunar Orbiter in 1967 but they did find a likely candidate in the images returned by the Clementine 1994 mission. It was a 1.5km wide crater with a fresh-looking layer of material surrounding the crater and the size was consistent with the energy from the observed flash.

Photo Courtesy JPL,  Dr. Bonnie Buratti, Lane Johnson

At this point it appears that the mystery has been solved but there are detractors who have found images of the Buratti/Lane crater in photos taken by two ground based telescopes before 1953, which rules out that crater as having been formed by Stuart’s Event. It was also ruled out by the editors of Sky and Telescope magazine who carefully measured the image of Stuart’s Event and determined that it was centred 30km from the Clementine candidate.

Maybe the Moon Zoo users can find this elusive crater if it exists! The following image shows the general area where the flash was seen. The final link under the “References” heading below contains coordinates of where the impact may have occurred.
Unfortunately, it appears that there is not complete coverage of the area by LRO – some areas do not have NAC images so the search will be difficult.
If you do find any candidates for Stuart’s Crater please post them in the Moon Zoo forum.



A good overview of the whole story with images of the event will be found here:
Stuart’s Event, Bright Flare, November 15, 1953

The following journal contains a re-publication of the original Strolling Astronomer article by Dr. Leon Stuart (page 21)
Journal of the Association of Lunar & Planetary Observers, Vol 45 Number 2

This strange link contains more images of Stuart’s Event and also coordinates of where the impact may have occurred. Scroll down within the page and it has maps of the lunar surface with the area where the impact is suspected to have occurred highlighted.
1956 Lunar Path Light?


Unusual features on North Massif

In January 2013, Moon Zoo user jaroslavp posted some interesting images in the Interesting terrain thread.

The images are from the base of the North Massif feature, close to where the Apollo 17 astronauts landed in the Taurus-Littrow valley. This image gives an overview of the NAC image from which the other images were taken (Note: North is at the bottom!):

The following images are from the marked area.

This image shows two areas with irregular boundaries – I can’t imagine what sort of process formed them.

NAC: M162107606RE Latitude = 20.2 Longitude = 30.7

Close to the previous image is this area showing odd striations and cross-hatching on the surface, possibly caused by entrained debris flow from an impact event. This may also explain the strange features in the previous image. The impact event that created the Serenitatis Basin may have been the event responsible.

Jules recently posted an Image of the Week about the Taurus-Littrow valley which has a great overview image showing the North and South Massifs: Moon landing at Taurus-Littrow

Taurus-Littrow (Wikipedia)

Approach to Taurus Littrow Valley (LROC)

Proclus lava flow

I was exploring Proclus crater recently and spotted a diamond-shaped flow of lava in the south-western region which is shown below.

Proclus crater is about 28km in diameter and is one of the brightest craters on the Moon, second only to Aristarchus. It has a bright ray system which is asymmetric, probably caused by a shallow-angle impact.

NAC strip: M104211600RC Overview of lava flow.

Edge of lava flow showing cracks, melt pools and boulder erosion.

‘Incoming!’ LPOD lunar photo of the day, 31 Jan 2006

Has a good overview of the creation of Proclus crater and its asymmetric ray system.

December 14: The final EVA

The final excursion on the lunar surface took place on the 14th December [GMT] and lasted over 7 hours. In all, 66 kgs of basalts, rock and soil samples were collected, many gravimeter measurements were taken and results from several experiments were recovered for return to Earth. As part of the Lunar Seismic Profiling Experiment explosive packages were left on the surface and were detonated remotely after liftoff of the ascent stage. This experiment consisted of an array of four geophones, three of which formed a triangular array about 100 metres on a side with the fourth geophone in the centre of the triangle. Eight explosive packages were placed around the geophone array at distances ranging from 0.1 to 2.7 km and these were detonated remotely once the astronauts were clear of the lunar surface. The signals from these explosive events plus the impact of the Apollo 17 LM at a range of 8.7 km from the array were used to create a model of the near surface lunar structure.

One of the Lunar Seismic Profiling explosive charges with radio antenna deployed [NASA]

Lunar Seismic Profiling Experiment

A plaque located on the landing gear of the lunar module was unveiled before the crew entered the module for the last time.

Apollo 17 plaque


Apollo Basin

Apollo Basin is a large (538km), double-ringed impact crater on the far side, at Latitude: -36 and Longitude: -152. The feature was named in honour of the Apollo program and many individual craters within the Apollo Basin are named after the astronauts lost on the Space Shuttles Challenger and Columbia.

The Apollo crater is superimposed on the huge South Pole-Aitken basin, one of the largest impact structures in the solar system and more than 8km deep. The impact that created the Apollo Basin may have exposed a portion of the Moon’s lower crust (see the Lunar Networks link below for more information).

This crater was selected as one of the fifty sites for LRO to investigate for future exploration of the Moon as it contains rare farside mare deposits in close association with the bright highlands materials found on the basin’s inner ring of mountains.

Image from ACT-REACT, centred at Latitude: -31.558 Longitude: -141.174, showing craters named after astronauts.

Image mosaic from USGS Map-A-Planet

The images in the last two links below are well worth a look!

Apollo Basin (NASA)

Challenger Astronauts Memorialized on the Moon

Apollo Basin – Lunar Networks

Apollo Basin – LOLA Image

Apollo Basin – LPOD

A beautiful ray crater on the far side

This week we’re featuring yet another crater posted by Moon Zoo user kodemunkey, this one is on the far side near crater Lents Lenz and has a wonderful white texture around the central impact area. It also has some areas of “black stuff” around the edge of the crater. We have a “black stuff” project on the Moon Zoo forum here: TLP Project – Black Stuff

from NAC strip: M186541565RC
Latitude: 3.3, Longitude: -100.3

Black stuff on the northern edge of the crater.

Detail of debris flow down the crater wall.

This unnamed crater is mentioned in this article where it is called the most beautiful raycrater of the entire moon’s surface.

See LPOD lunar photo of the day, 12 December 2007 for a great image of the crater.

Exploring the Marius Hills Region

Moon Zoo user kodemunkey posted a great image of a fresh white crater with garcinia residue in the Interesting terrain thread on the 29th September 2012.

NAC Strip: M170877942RE Latitude: 9.4 Longitude: -48.3 (close to Marius V crater)

After finding the fresh white crater on the NAC strip I did a bit more exploring and found a crater with a good example of “black stuff” – see the TLP Project – Black Stuff for more information.

“Black Stuff” – same NAC strip as above.

The Marius Hills region of the Moon is full of interesting formations and contains many volcanic domes, cones and rilles, and is well worth exploring.

I looked at a wider view of the area using the ACT-REACT tool and discovered the Rima Suess rille which runs for about 200 km across this region. There is a strange elongated “craterlet” to the north-west of the rille which appears to be connected to it in some way. I can’t find much information about this craterlet and it would be interesting to know how it formed and if it is related to the Rima Suess at all.

from ACT-REACT tool. Craterlet is at Latitude: 8.65 Longitude: -48.66

Anaxagoras Crater

Anaxagoras crater is close to the north pole of the Moon, is about 50 km in diameter and is at coordinates 73.4 N / 10.1 W. There is a lot of impact melt within the crater which creates some interesting terrain. The interior of the crater was selected as a region of interest for human exploration by the Constellation program as this region may help in the study of the global magma ocean concept and the evolution and development of the lunar crust. The central peak of Anaxagoras crater is composed of pure anorthosite which probably formed when the Moon was molten and the lighter material floated to the top and solidified.

Anaxagoras crater seen by the high-definition camera on Japan’s lunar orbiter Selene-1 in 2009. [JAXA/NHK/SELENE]

A dome within Anaxagoras crater. Most of the boulders in the image are between 10 and 30 metres in size.

Quote:(author=LROC News System) Additionally, there are several hills and bulges that are covered with clusters of boulders. There are no impacts in the melt sheet that might account for the boulder clusters, thus a possible explanation is that the boulders are eroding out of the impact melt that covers these hills. These boulders look similar to boulder clusters eroding out of wrinkle ridges in the mare; are they the result of a similar process?

See Impact melt in Anaxagoras crater below.

A boulder precariously balanced on the edge of a cliff or steep slope.

Boulder group resembling a face.


Impact melt in Anaxagoras crater (Lunar Networks)

Anaxagoras Crater – LOLA image

Anaxagoras Exterior Melt (LROC)

Lunar Anorthosite

A Mystery in Mare Crisium

The Luna missions were a series of unmanned spacecraft missions sent to explore the Moon from orbit and on the surface, by the Soviet Union between 1959 and 1976.

Three of these missions, Luna 16 (September 1970), Luna 20 (February 1972) and Luna 24 (August 1976), are of interest because they returned soil samples from the surface of the Moon. These missions returned 0.33 kg (about 12 ounces) of lunar soil in total and the descent stages of the spacecraft still remain on the Moon and can be seen in LROC images (see LROC: Lunar Sample Return Missions below).

Luna 16 returned 101 grams from Mare Fecunditatis. A sampling arm was used to drill into the surface to collect soil which was then placed into a sample container on top of the spacecraft which later launched itself off the luna lander and returned to Earth.

Luna 16 spacecraft [National Space Science Data Center]

Luna 20 was the second successful sampling mission and the material returned from the Apollonius Highlands was similar in composition to the samples returned by the Apollo 16 astronauts.

Luna 23 and Luna 24 were both sent to sample Mare Crisium but Luna 23 failed (it may have landed on a slope and fallen over). Luna 24 was successful and sent back a 170 gram sample.
The Soviets originally thought that the two landers were within a few hundred meters of each other but using the images of the landers found on NAC images they appear to be about 2400 meters apart (see LROC: Mare Crisium Failure then Success below).

Luna 24 [NASA/GSFC/Arizona State University]

The sample material returned by Luna 24 was different from what was expected by the scientists. They had made certain assumptions about what the material should be, based on remote sensing data of Mare Crisium and their understanding of what Mare material should consist of. This mystery was only solved when the Luna 24 lander was found on NAC strip M174868307LC and shown to be sitting on impact ejecta from a nearby secondary crater. The sample returned to Earth consisted of material from beneath the surface of the Mare which had been excavated by the secondary impact.

Quote: (author=Jeff Plescia, LROC) The returned Luna 24 sample surprised scientists as it had unexpected characteristics based on the understanding of Mare Crisium geology at the time. Most importantly, the titanium content and the maturity (or the amount of time the sample was exposed to the space environment) of the sample material were different than anticipated. But how could this be? Based on the geologic context of the lander, the reason for the difference may now be understood. With the precise location of the landing site now known, the LROC images show that the mission sampled impact ejecta from a nearby 64-meter diameter crater. That crater has excavated below the surface bringing up material from deeper lava flows that had not been previously exposed to the space environment. Thus, the Luna 24 sample may not represent nearby Mare Crisium surface materials observed using remote sensing techniques, but rather the subsurface which was only exposed to the space environment for the relatively short time. It’s amazing what geologic context can tell you!

The Luna 24 mission may help with another Moon mystery – according to Soviet Moon Lander Discovered Water on the Moon in 1976 the sample returned by Luna 24 contained 0.1 percent water by mass.


LROC: Lunar Sample Return Missions

LROC: Mare Crisium Failure then Success

Wiki: Luna Programme

Luna 24

Lunar erosion at work?

On 4th July 2012 user kodemunkey posted an interesting image in the Interesting terrain thread and suggested that it was a ‘Possible example of the stages of lunar rock erosion?’
I’m not a lunar geologist so can’t tell if this formation is caused by erosion or not but it does look interesting. The centre of the image appears to be a crust formed from a lava flow and looks like it is eroding away at the sides as slabs of the lava crust are splitting away.

Erosion does occur on the Moon but the process takes a lot longer than the erosion processes on the Earth. The solar wind and micro-meteorite impacts appear to be the main drivers of erosion on the Moon today as well as the big temperature change between day and night which weakens and breaks up rock. See the link What causes erosion on the moon? at the end of this post for further information.

NAC: M167417084LE Latitude: 5 Longitude: 120
Near King crater, far side.

From the same NAC strip, an image of boulders which have split probably due to temperature change stress.

A similar image of boulders ‘eroding’ from the edge of a lava crust was posted by user ElisabethB a month later on 4th August 2012 in the same thread.
This is from the Aristarchus region.

NAC: M114267211RC

Useful Links

What causes erosion on the moon?

The Surface of the Moon

Quote: Over billions of years, collisions with meteoroids, large and small, have scarred, cratered, and sculpted the lunar landscape. At the present average rates, one new 10-km-diameter lunar crater is formed every 10 million years, one new 1-m-diameter crater is created about once a month, and 1-cm-diameter craters are formed every few minutes.