Today, despite many lunar missions, we still don't know for sure if there is enough water on the Moon to be useful for supporting human life. The Mass Spectrometer Observing Lunar Operations (MSolo) is a scientific instrument developed by NASA that has the potential to resolve this once and for all.
NASA will use MSolo to identify molecules bouncing around near the surface of the Moon, i.e. in the Moon's "exosphere". If water molecules are present in the exosphere in sufficient quantities, scientists can reasonably infer the nearby quantities of water bound up in the Moon's regolith.
MSolo payload units are already scheduled to fly on three of NASA's upcoming Commercial Lunar Payload Services (CLPS) robotic moon landing missions:
- In Q4 of 2021, on Astrobotic Technology's, landing at Lacus Mortis
- In late 2022, on Intuitive Machines' Mission 2 (IM-2), landing at a polar region
- In late 2023, on the Volatiles Investigating Polar Exploration Rover, (VIPER) mission to the Moon’s South Pole (also on an Astrobotic lander).
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| MSolo Instrument (Image credit NASA) |
Astrobotic Technology's Peregrine Mission One will characterize the lunar exosphere throughout the illuminated period of the first lunar day (about two weeks duration), to understand the release and movement of volatile species as a function of time. Directly after the lander touches down the local exosphere is expected to show a high signal from the lander's propulsion system exhaust. The measurements are then expected to show a decay in exosphere density from its post-landing peak. During the measurement period, other stimuli creating transient increases are also hoped to be observed, e.g. when mechanisms or other payloads of the lander are active or if any meteorites land nearby.
As Peregrine Mission One will land at a non-polar region, no substantial water signature is expected. However, the two subsequent missions will be landing near the South Pole where satellite-based evidence suggets substantially higher amounts of water are present in the regolith.
On the VIPER mission MSolo will be used in a similar way but at multiple locations near the Moon's South Pole thanks to it being mounted on a mobile rover.
MSolo is a modification of a commercial off-the-shelf mass spectrometer. The commercial product is INFICON's Transpector MPH, a residual gas analyzer used in the semiconductor manufacturing sector here on Earth. It is a quadrupole type mass spectrometer. Like all mass spectrometers it measures the mass-to-charge ratio of ions. NASA worked with INFICON to develop a new version that is space capable. It has a new space-qualified instrument compueter, modified control electronics and a new strutural housing to resist the loads of launch and provide adequate thermal protection for hte two-week landed mission duration. A new releasable dust cover was also developed to protect the instrument from dust and debris kicked up during landing.
MSolo's weight is <7.5kg.
MSolo will not be the first mass spectrometer to operate on the lunar surface. That honour goes to an Apollo era instrument called LACE, which flew on Apollo 17 in 1972. LACE was a miniature magnetic deflection mass spectrometer deployed on the surface and oriented to intercept and measure the downward flux of molecular gases. This instrument operated for 9 months, supported to survive the lunar nights by a SNAP-27 Radioisotope Thermoelectric Generator (RTG). LACE's measurements were routinely swamped by artifacts emanating from the nearby Apollo lunar module descent stage and other abandoned equipment during the lunar day. Water was not detected in its measurements due to the high backgrounds both inside and outside the instrument, and its relatively low sensitivity compared to modern day mass portable mass spectrometers like MSolo.
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