Jahnavi Shah

PhD Student, Planetary Science

Lunar Love

Lunar Eclipse 2019

Starting off with some pictures of the Super Wolf Blood Moon on January 20th. I decided to embrace the -30 oC  weather and went to the Cronyn Observatory to see the eclipse (mostly worth freezing my toes off). The first picture was taken by my phone looking into the telescope at Cronyn. The second photo was taken by an astrophotographer friend of mine in Toronto.  

Earth and Moon impact flux increased at the end of the Paleozoic (Mazrouei et al., 2019)

A new study was published in Science reports that the rate of large crater formation on the Moon has been 2-3 times higher over the last ~290-300 million years than it had been over the previous 700 million years. This increase in impact flux could be related to collisions taking place in the asteroid belt around 300 Ma which created debris that could have travelled into the inner solar system. However, the exact reason for this spike in impact rate is unknown. 

The neat part about studying lunar surface (and craters) is that it provides information about the Earth as well. Because of their close proximity, their impact flux should be very similar. This challenges the theory that terrestrial craters were lost through erosion which makes it difficult to calculate an impact rate. The reason there are fewer older terrestrial craters (large craters), even on its most stable terrains, is because of the lower impact rate 290 Ma, and not solely because of erosion. 

Here’s a clip 1 billion years of Moon impacts converted into music by SYSTEM sounds:

This study was done using data from LRO’s thermal radiometer, Diviner, which created day and night surface temperature maps of the Moon. Diviner was used to create a rock abundance map of the lunar surface. This is done by looking at the radiated heat during the lunar night when large rocks are warm whereas the regolith is cooler. This showed that large craters formed in the last billion years are covered by boulders while older crater have fewer rocks (because they are broken by by micro-meteoroid bombardment over tens to hundreds of millions of years). A paper by Ghent et al., 2014 calculated the rate at which lunar rocks break down into soil which revealed an inverse relationship between large rock abundance near a crater and the crater’s age. This technique was used to date 111 rocky lunar craters (D  ≥ 10 km) younger than about a billion years. The 10 km was chosen as a minimum size because those craters have penetrated the surface regolith enough to excavate large blocks from the bedrock.

Regression of lunar crater age versus 95th percentile rock abundance.
Geographic distribution of 111 rocky (young) craters with D ≥ 10 km between 80°N and 80°S on the Moon, scaled by size and color coded according to age. Orange indicates craters younger than 290 Ma; pink indicates craters 290 to 580 Ma old; dark blue indicates craters 580 to 870 Ma old; yellow indicates craters 870 to 1160 Ma old; and white indicates craters older than 1160 Ma. 

3D printing on the Moon 

A study supported by ESA Discovery & Preparation investigated the use of 3D printing in order to construct, expand, and maintain a lunar base. A lunar base is a way to establish a sustainable long-term presence on the moon and will be important in order to carry out long-term experiments (e.g. learning about the lunar environment assessing health impacts of living in space, etc.). With a lunar base, the goal is to be as Earth-independent as possible and thus, necessary structuers and equipment will eventually need to be made in-situ and on demand. The most reasonable way to do this is use 3D printing technologies with lunar regolith as the input material. However, not every structure can be 3D printed and not every 3D printing process is suitable for every pupose. Past studies on 3D printing of materials for a lunar base were focused on habitat structure. But, this new study looked into every aspect of construction and operation of a lunar base. 

Project URBAN, “Conceiving a lunar base using 3D printing technologies”, is led by Germany’s OHB systemsSonaca SpaceLiquifier System Group and COMEX. It studied all available printing materials and techniques to create a searchable databse to find the most efficient way of producing specific items using resources available on the Moon. The techniques were selected based on its interest for lunar exploration due to their versatility, space-readiness and ability to process a range of materials. 

1. Solar sintering: concentrates sunlight to shape lunar regolith into a variety of objects, mostly for infrastructure (e.g. habitat, landing pads, and dust protection walls). 

2. Electron beam additive manufacturing: uses a vacuum to create an electron beam, the raw material is placed under the vacuum and is fused together from heating by the beam. This can be used to produce large metal parts. 

3. Fused filament fabrication: uses a continuous filament of a thermoplastic material. It can create a wide range of materials and has already been tested in low gravity conditions. 

4. Lithography-based ceramic manufacturing: can use lunar regolith to create ceramic intems with precise dimensions. 

Materials processed by the four selected 3D printing technologies. 

The team has 3D-printed screws, gears, and assorted other small objects from a simulated moon-dust and a light-activated glue-like chemical binder. These objects have a strength and consistency similar to a ceramic, and with a precision of 50 microns.  

Additionally, I recently heard a podcast episode on this topic (unfortunately can’t remember the podcast or scientist name) and they mentioned that even though 3D printing could prove to be very useful in building a lunar base, it does require a lot of time. A possible solution to this could be sending robots to operate the 3D printers and start constructing the foundations of the lunar base and then sending humans. This would be more time and cost efficient. 

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