Overview:

The mission is called Parthenos, after the attendant of Artemis that was eventually granted immortality by her brother and became her companion and chief hunter.

Parthenos is a rover which will utilize data from lunar satellites to land on a pre-selected site and will use its on-board equipment to analyse the rocks and soil present at that location. This will not only serve as further analysis, but will also help in refining landing site options for the future 2024 Artemis mission, much like how the immortal huntress would have done for the goddess.

Most of the data required for preparations will be taken from the Lunar Reconnaissance Orbiter (LRO), which has mapped 98.2% of the lunar surface at 100-meter resolutions, giving us ample topographic data to determine which would be ideal sites for the rover to traverse. Other sources that we will be using include data from the Clementine Probe from 1992 and other public access data from the Lunar Science Institute.

Aim of the Mission and Search:

The Parthenos mission intends to serves the Artemis 3 crewed mission in 2024 and further Artemis missions in the future, and thus will be primarily searching for water and other minerals in the regolith that would be useful in the construction of a crewed lunar habitat. This would greatly reduce EVA hours and provide incoming missions with a more refined guideline for any further research and what instrumentation they might intend to bring.

Section 1: Deciding the Landing Site

The map used for Parthenos is the 2009 LRO map provided in false colour by Arizona State University in Tempe. It shows the surface shape and features over nearly the entire moon with a pixel scale close to 100 meters. A single measure of elevation (one pixel) is nearly the size of two football fields placed side-by-side[2].

Figure 1: False colour map of the moon using data obtained by the LRO

A closer analysis of the topographic maps of the lunar south pole - provided to us by the data obtained from the LRO - show us that the ideal landing site based on surface and elevation would be the area triangulated by the Sverdrup, Slater and Wiechert P craters. According to a quantitative illumination map created for the year 2020 using Clementine data, the mentioned area has a 60-75% illuminated time fraction[3].

The lunar south polar craters and maria are rich in minerals, the primary ones being silicates and metal oxides. Silicates can be used for the construction of ceramic tiles and metal oxides such as titanium dioxide can be used for deodorizing properties, things that a crewed habitat might use.

Given below is a table of the most prominent compounds found in the lunar south pole, with the next section focusing on how Parthenos will search for them.

The following compounds are listed in descending order of prevalence in lunar soil (regolith) and crust:

The chosen landing site (between Sverdrup, Slater and Wiechert P craters) is somewhere between the maria and the highlands of the moon, since the average elevation height is 105 m. While there isn’t much difference between the percentage of silica, there is a marked difference in the fraction of abundance of all other materials apart from sodium oxide[4]. While the above materials can be used by a crewed habitat for minor purposes (without the aid of a factory that would utilize these materials to transform them into much more valuable resources), lunar regolith can be used directly for radiation shielding of a crewed habitat.

The chosen landing site is also deemed to be rich in water-ice, with previous orbiters providing evidence of the existence of water-ice on the lunar south pole. Parthenos aims to confirm and refine the data collected by these orbiters, thus saving astronaut work hours and astronaut EVA time.

Section Two: Analysis Methods

For the compounds found on the chosen landing site, the following methods can be used for invasive and non-invasive analysis of the Moon’s surface and crust.

Non-invasive Methods:

1. X-Ray Fluorescence: is the emission of "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. Parthenos will use the PIXL (Planetary Instrument for X-ray Lithochemistry) that is also onboard the Mars 2020 rover[5].
   
   PIXL uses microfocus x-ray fluorescence to rapidly measure elemental chemistry at sub-millimeter scales by focusing an X-ray beam to a tiny spot on the target rock or soil and analyzing the induced X-ray fluorescence. Scanning the beam reveals spatial variations in chemistry in relation to fine-scale features such as laminae, grains, cements, veins, and concretions.
   
   High X-ray flux enables high sensitivity and short integration times: most elements are detected at lower concentrations than on previous landed payloads to the Moon, and several new elements can be detected that were not previously detectable. This allows for rapid scanning so that PIXL can reveal the associations between different elements and the observed textures and structures. It will be utilising a sensor head placed on the robotic arm of the Parthenos rove. The sensor head includes an x-ray source, X-ray optics, X-ray detectors, high-voltage power supply (HVPS), as well as a micro-context camera (MCC) and light-emitting diode (LED).
   
   The PIXL can detect the following elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Rb, Sr, Y, Ga, Ge, As, and Zr, with important trace elements such as Rb, Sr, Y and Zr detectable at 10 ppm level.

The combined effect of PIXL’s speed, sensitivity, resolution, coverage/targeting, and measurement flexibility allows it to search efficiently and locate the places of interest and to observe small patches of clean rock, saving over 40+ hours of astronaut EVA activity.

Invasive Methods:

1. Core drilling: Parthenos will be using a core drilling unit similar to that on the Rosalind Franklin rover[7]. That entails the following specifications:
   1. Drill Tool - About 700 mm long, equipped with the sample acquisition device, inclusive of a shutter, movable piston, position and temperature sensors, etc. and with the required optical fibre, lamp, window, and reflector.
   2. Four Extension Rods - About 375 mm each, designed to extend the penetration length to 1.5 meters. They are provided with electrical contacts and guarantee the transmission of the optical signal to the spectrometer
   3. Rotation-Translation Group - Including the sliding carriage motors and sensors, the gear mechanisms and the optical rotary joint.
   4. Drill Box Structure - Including the clamping system for the rods and the automatic engage-disengage mechanism for the rods. On the drill box structure the spectrometer and the drill proximity electronics are installed.

The collected samples from the invasive techniques will then be sealed in nitrogen gas filled titanium containers. Titanium ensures lightness and reduces the weight of the rover (which in turn will lower the strain on the engine and reduce power depletion) while nitrogen, due to its inert nature, will keep the sample and its chemical components intact.

Section Three: Benefits of the Mission

Parthenos will be aiding the Artemis mission by significantly reducing the number of astronaut hours and EVA astronaut hours. Most of the data will be analysed in situ and sent back to the team back on Earth, which would help the Artemis mission team refine future landing sites and possibly reduce equipment on board.

1. The last numbers for lunar sample collection are from the Apollo Era, when the average time spent by astronauts on collection was 21 hours over the course of their entire mission. Apollo 11 brought back 22 kilograms of lunar material, most of which was rocks and lunar soil. However, Parthenos will greatly increase the quality of samples collected and the reduce EVA time by completing preliminary analysis and sample collection (invasively and non-invasively) by entirely eliminating the above EVA time. The preliminary analysis also cuts down on another ~20 hours of astronaut work and allows them to complete more in depth laboratory tests on the sample.
   
2. Since most element detection will be non-invasive, that will reduce payload weight by about 40%. The rest 60% of the collected samples will comprise of 30% of lunar regolith to be further tested for radiation shielding properties, 30% of mineral rich samples that will be tested for extraction and use, and the remaining 40% will be samples to test for extraction and use of water ice.
   
3. Currently, it costs $1,000 to put a pound of cargo into space by using launchers such as the Falcon Heavy. By reducing the payload taken back by the astronauts from ~400 kg to around 250 kg, Parthenos aims to reduce each mission’s cost by $68,000.

Sources:

1. https://www.nasa.gov/mission_pages/LRO/news/lro-to...
2. https://www.lpi.usra.edu/lunar/lunar-south-pole-atlas/ - Stopar J. and Meyer H. (2019) Topographic Map of the Moon’s South Pole (80°S to Pole), Lunar and Planetary Institute Regional Planetary Image Facility, LPI Contribution 2169
3. Bussey D. B. J., McGovern J. A., Spudis P. D., Neish C. D., Noda H., Ishihara Y., Sørensen S.-A. (2010). "Illumination conditions of the south pole of the Moon derived using Kaguya topography". Icarus. 208
4. Taylor, Stuart R. (1975). Lunar Science: a Post-Apollo View. Oxford: Pergamon Press
5. https://mars.nasa.gov/mars2020/mission/instruments...
6. http://lasp.colorado.edu/~horanyi/nlsi/AMES_2008/N...
7. https://exploration.esa.int/web/mars/-/43611-rover...
8. https://www.nasa.gov/centers/marshall/news/background/facts/astp.html