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)
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?
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
Pits and skylights
Areas of Near Constant Sunlight at the South Pole
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.
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:
TO BE DETERMINED”
Here’s a reminder the Moon Zoo science goals- and what our clicks are being used for.
1. To improve our knowledge of the production of small lunar craters by gathering information about their numbers and dimensions. This can be used to improve lunar maps and coordinates.
2. To calculate the age of different lunar surfaces (e.g., mare, impact melt sheets, highland crust) by comparing the number and sizes of impact craters. The more cratered a region is the older it is. Knowing the age of different surfaces allows us to build up a history of the geological processes on the Moon, in particular its temporal thermal and magmatic history. What we learn about these processes on the Moon we can then apply to other small rocky planetary bodies.
3. Results from Moon Zoo could also assist in the development of automated computer crater counting systems, and to help understand how image viewing geometries influences crater counting studies.
4. To determine variations in lunar regolith thickness by assessing the presence of boulders around crater rims.
5. To identify unique and unusual morphological features that help us to better understand the geological diversity of the Moon. Recording these featured will help to develop a database of interesting morphological features (for example, boulder tracks, fresh white and dark haloed craters, crater chains, elongate craters and pits etc) for the lunar science community to use.
To produce a boulder density hazard map to assist in identifying suitable landing sites for future human or robotic lunar missions.
- To produce peer-reviewed science.
- To promote lunar and planetary science through using Moon Zoo as an educational and public outreach tool.
- To identify small, highly elliptical craters that may have preserved meteoritic material.
- To assess degraded craters according to variations in user measurements and produce maps of crater degradation states.
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!
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.
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!
Sketching the Moon is an ancient and still widely practised art. It requires patience and plenty of time and must be an excellent way to familiarise yourself with the lunar terrain. Cameras are very good at picking up subtle detail and shading missed by the human eye but the advantage of a drawing is that it is a faithful representation of what you can actually see through the eyepiece. For this week’s Image of the Week I have borrowed the most recent LPOD (Lunar Picture of the Day), a drawing of Rupes Recta (the straight wall) in Mare Nubium at 22.1°S 7.8°W . This 110 km long linear rille is 240-300 m high and 2.5 km wide. Although not very steep the rille casts a dramatic shadow when illuminated by a low Sun.
Rupes recta, and craters Birt, Thebit, Thebit A and Thebit L. Both images have been rotated so that south is up.
The LROC image was taken at a much higher illumination angle but lunar features clearly match and the amount of detail in the drawing is remarkable. In these images the trio of overlapping craters Thebit, Thebit A and Thebit L are to the left of Rupes Recta and Birt crater is to the right.
After 13 days in space Eugene Cernan, Ronald Evans, and Harrison (Jack) Schmitt aboard the Apollo 17 command module Challenger parachuted to a safe splashdown at 19:20 GMT on 19 December 1972, 648 km southeast of American Samoa. The last humans to have walked on the Moon.
There is still much to learn from the Apollo 17 mission. Moon Zoo needs your help to explore the Apollo 17 landing site. Celebrate the anniversary with us. Go to http://www.moonzoo.org/ and start clicking! Follow “live” mission tweets from @moonzoo