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The Orbital Index

Issue No. 169 | May 18, 2022

🚀 🌍 🛰

Growing in Moon dirt. Over 50 years after the first lunar samples were returned, a first attempt was recently completed to grow plants in actual honest-to-goodness regolith from the surface of the Moon! To determine whether regolith’s uses as an in-situ resource could include acting as a growing medium (paper), Arabidopsis thaliana (thale cress) seeds were germinated in samples from Apollo 11, 12, and 17 sieved to a <1 mm particle size and then grown for 20 days before being ‘harvested’ (A. thaliana is edible, but none of this will get masticated). Each sample contained 900 mg of regolith, 2-4 seeds, and was mixed with water (although the Apollo 11 and 12 samples unexpectedly proved hydrophobic) with an additional nutrient solution added daily. Meanwhile, a control group was grown nearby in lunar regolith simulant JSC-1A. “The answer to the first question is a resounding yes. Plants can grow in lunar regolith. They were not as robust as plants grown in Earth soil, or even as those in the control group grown in a lunar simulant made from volcanic ash, but they did indeed grow.” Plants in the Apollo 11 samples fared the worst, possibly due to the maturity of the regolith gathered at that site—mature regolith has been bombarded by solar wind and micrometeoroids until it has been pulverized into small grains, which generates high levels of nanophase iron. Apollo 17’s immature regolith tended to grow much larger plants. However, all regolith-grown plants displayed significant amounts of stress—similar to plants that have grown in soil with high levels of salt or heavy metals—when compared to the JSC-1A plants. (This highlights our lack of understanding of how well lunar regolith simulants represent different characteristics of actual lunar material.) But despite all this, the plants did grow! These results are promising, but before we can start growing lunar salad we’ll need to do more characterization in different types of regolith and optimization of plant strains. 🌱

Snapshots throughout the experiment of thale cress samples grown in three different Apollo mission regolith samples and JSC-1A regolith simulant.

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From Xometry, a detailed guide to direct part marking - a great way to ensure traceability while also enabling automatic part detection and easy assembly. From laser marking to screen printing to bagging and tagging, part marking is an easy and useful addition to your toolset!

For the CST-100 Starliner, maybe the third time's the charm? Remember Starliner? Along with SpaceX, Boeing was tasked through NASA’s Commercial Crew Program with carrying astronauts to and from the ISS. While SpaceX’s Dragon has now successfully been doing so for two years, Starliner… not so much. In 2014, Boeing was awarded $4.2 billion by NASA to build, test, and fly the Starliner, while SpaceX received $2.6 billion. After Starliner failed to reach the ISS in Dec 2019, NASA identified 80 corrective actions. With those completed 18 months later, Boeing set up to launch their second uncrewed flight, but stuck valves in the propulsion system sent the spacecraft back to the shop for another 8 months. Confident that the valves have now been unstuck (but also planning a redesign and in a tiff with their designer Aerojet), Boeing is scheduled to attempt OFT-2, another uncrewed demonstration flight to the ISS, tomorrow on an Atlas V from Kennedy Space Center. Boeing spent $410 million of their own money to cover remediations and this second flight, demonstrating again why fixed-cost awards are so much better than cost-plus ones like Orion and SLS.

Starliner headed to the launch pad earlier this month. Credit: Stephen Clark / Spaceflight Now

(Planetary Science) Papers.

  • Around 4.4 billion years ago, a Mars-sized protoplanet (called Theia) probably struck the Earth and the resulting debris formed the Moon. The newly formed Moon, covered in a sea of lava, was only about 4 Earth radii away and would have appeared 15x bigger in the sky than it does today. This early proximity and the tidal heating it generated may start to solve the “faint young Sun paradox,” helping to explain why the early Earth had liquid water and wasn’t frozen solid as it orbited a Sun that was only 70% as bright as it is today. (Tidal heating also caused the Moon to slowly spiral outward to its current, and still receding, orbit). Tidal heating falls off as the cube of distance, so when the Moon was much closer, the heating effect could have been over 3,000x stronger. (This would imply any oceans at the time had tides 2 km tall.) While tidal heating wouldn’t produce enough heat to completely solve the paradox, it can start to explain it.
  • The ‘Late Heavy Bombardment’ is the fairly well-accepted idea that there was a surge in planetary bombardment for a period after Theia’s impact and the Moon’s formation, about 3.9 billion years ago—leaving scars on the Moon (like Mare Imbrium), the Earth, Vesta, and other inner planets. The Nice model suggests that Jupiter fell into resonance with Saturn and caused Uranus and Neptune to shift outward during this period, disturbing asteroids and sending them plowing inwards. However, it’s also possible that “the bombardment was just the tail end of a longer, steadier wave of impacts from material that formed the inner planets in the first place.” If this is true, the composition of rocks formed during that period should look more like inner- than outer-solar system material. A new paper does this analysis, looking at the ratio of ruthenium and molybdenum in rocks returned by Apollo 16 and in lunar meteorites, and finds a more inner-solar-system ratio. The Nice model could still be mostly correct, but the giant planet resonance may have happened at a different time than previously thought.
  • Almost all helium-3 in the Universe formed shortly after the Big Bang. Because of this, detection of the rare isotope leaking out of Earth’s core hints at Earth having formed inside of a solar nebula, a location proportionately rich in this isotope. While a new paper estimates that only 2 kg of helium-3 leak out of the Earth every year, this leak rate indicates a core containing 1010-1012  kg of helium-3 and suggests that our solar system formed inside of a “thriving solar nebula, not on its fringes or during its waning phase.

News in brief. Colombia signed the Artemis Accords, the 19th nation to do so More rumors of a Globalstar + Apple partnership to provide satellite connectivity for future iPhones British Orbex revealed their 19 m tall, two-stage Prime rocket for smallsat launches Another batch of 53 Starlink satellites went to orbit, and then another less than 24 hr later Chinese iSpace had a third launch failure of their four-stage solid-fueled Hyperbola-1 vehicle The Russian military satellite launched on Angara-1.2 appears to be defective Eight microsatellites for the Jilin 1 high-res EO constellation launched on a Long March 2D US Senators Dianne Feinstein (D-CA) and Marco Rubio (R-FL) introduced a bill to create a Space National Guard, which sounds hilarious… but may be a reasonable way for the Space Force to retain personnel as they leave active duty  NASA announced that InSight’s mission will be forced to wind down by the end of the year due to decreasing solar power production—unless a friendly dust devil swings by to clean its panels off (which happened to Oppy and Spirit). 🌪


The distributed Event Horizon Telescope network captured its second direct radio image of a black hole, this time Sagittarius A* at the heart of our Milky Way. The glowing ring is the black hole’s photon sphere, containing photons that orbited the black hole many times before escaping. They found that the black hole is rotating—coincidently with its rotational axis pointing pretty much right at us— and that it has a mass of 4 million solar masses. 🤯