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Martian Double Craters

Over on Planet Four Talk moderator wassock found this Martian double crater in the HiRise images:

which can only have been created by 2 simultaneous impacts.

He messaged me to ask if we had found anything similar on the Moon and also sent a further image of a laboratory test of a high velocity simultaneous impact by 2 objects:

Here are some lunar doubles:

Messier A (on the left – most likely created by separate events)


Tres Amicis

None of these examples has the distinctive “equatorial” ejecta pattern of first 2 images which I have never seen on the Moon. Why might that be? Well, we know that Mars and the Moon differ geologically so maybe the type of impacted surface and bedrock plays a role. Did the impact take place when Mars was much wetter/ muddier than it is now? Mars also has a more dynamic atmosphere. Would any of these differences account for the distinctive formation of the Martian doubles and ejecta pattern? Maybe the angle and velocity of impact is relevant here too and these double craters form only from high velocity overhead impacts. Wassock says he has found more Martian examples. On a quick look at ACT-REACT quick map I can’t find any lunar equivalents. Can you?

Ten Cool Things Seen in the First Year of LRO

The Lunar Reconnaissance Orbiter will soon have been orbiting the Moon for 4 years. Here’s a reminder of ten cool things it “saw” in its first year.
From NASA’s mission pages.

The coldest place in the solar system

Astronauts first steps on the Moon

Apollo14 and the near miss of cone crater

Lukhnod 1 found

LOLA’s Lunar farside

Craters and boulders with Moon Zoo

Moon Mountains

Lunar Rilles

Pits and skylights

Areas of Near Constant Sunlight at the South Pole

Looking for the Kaguya impact

Kaguya – NASA

Forum regular JJ went hunting for the Japanese lunar explorer Kaguya impact site. Kaguya (or SELENE: SELenological and ENgineering Explorer) was launched 14 September 2007. Once in lunar orbit Kaguya released two smaller satellites into separate elliptical polar orbits: Okina (a relay satellite for communications) and Ouna (a Very Long Baseline Interferometry (VLBI) radio source satellite for supporting radio measurements). As well as its 2 sub-satellites Kaguya carried 13 scientific instruments including a lunar Magnetometer,  a Gamma ray spectrometer, a Lunar Radar Sounder and an Earth-looking Upper Atmosphere and Plasma Imager. the mission lasted 18 months after which Kayuya was sent into a series of lunar orbits prior to a controlled impact on 10 June 2009. The impact site was conveniently in darkness at the time allowing the impact flash to be seen from Earth. Okina impacted on the far side on February 12 2009. Ouna is still in orbit.

The Kaguya mission amongst other things has improved lunar global topography maps (also used by Google to make Google Moon 3D), a detailed gravity map of the far side, and the first optical observation of the permanently shadowed interior of south pole Shackleton crater.

The Kaguya impact coordinates are well documented but we couldn’t recall seeing a high resolution view of the impact site from LRO. What JJ was looking for was a small fresh impact which would have exposed some fresh lunar regolith leaving a white scar with a blackened centre where debris may remain.

The Kaguya website gives the impact coordinates as E80.4, S65.5. Here’s the location:

This indicates an impact site on the wall of an unnamed crater near crater Gill. Part of crater Gill is top left of this image provided by ESA:

Using the ACT-REACT Quick Map tool JJ located the unnamed crater.

And found a likely impact site on the rim of a smaller crater within the unnamed crater.

And finally – a potential impact site with a centre geodetic diameter of 23m:

We think it’s definitely a contender.

Departure from: Moon

Shamelessly copied from today’s LPOD (Lunar Photo of the Day), this is the Customs and Immigration form signed by Apollo 11 astronauts after returning from the Moon. Yes – even the first lunar visitors had to go through customs on the way back!

My favourite bit:

“Any other condition on board which may lead to the spread of disease:

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?

Seeing is Believing

The Apollo Lunar Surface Journal contains hundreds of images. Dig deep and you can find some surprises. Take this secret moon base for example. Note the circular access road and the living quarters annex at 11 o’clock.

Because that’s what it is – right? Wrong! A classic case of mis-direction and jumping to (very wrong) conclusions! Far from being yet another lunar conspiracy target this is actually a photo of the Apollo 15 Command and Service Module in lunar orbit over the Sea of Serenity. It was taken from the Lunar Module just before it began landing manoeuvres. You can see half of Bessel crater on the right in the image below.

More images can be found on the Apollo 15 page.  Be careful how you interpret them!

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)

Flying over Taurus-Littrow

The LRO took many images of the Apollo 17 landing site at Taurus-Littrow. Here is a glorious oblique “spaceship-eye” view of the Sculptured Hills and massifs surrounding the landing site taken from from M1096343661R and L. The position of the Lunar Module is marked on the second image.

Two NAC images have been stitched together and the aspect ratio tweaked to around 4:1. (click image for larger version.)

Can you find the Moon?

A puzzle for you this week. Can you tell the difference between a moon, a planet and minor planet? Below are images of craters on our Moon, Vesta and Mercury but which is which? Superficially very similar but there are differences. Click on the letters below for links to reveal the answers.

Don’t peek until you have had a guess!

a  b  c

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.