Background

Moonlink is an educational program designed for middle and high school students, giving them the opportunity to become actively involved in the Lunar Prospector mission. Schools have the opportunity to buy a piece of the moon to research and collect data. As students research the Moon, they are helping explorers discover new things.

The mission is controlled by NASA’s Ames Research Center. It is uses the Lunar Prospector spacecraft, which was launched on January 6, 1998. Lunar Prospector orbited the Moon at a 100 km average altitude, having a circular polar orbit with a period of 118 minutes. The mission lasted 18 months, concluding with a deliberate crash landing in a crater near the lunar south pole last July. The satellite gathered data on the Moon’s surface composition, gravity and magnetic fields. The discoveries of Lunar Prospector will be used to understand the origin, evolution, current state, and resources of the moon. The mission cost $51 million (in 1992 dollars).

The first part of the Moonlink process involved selecting a moon site to purchase. Each site is 150 km by 150 km. Sites are available all over the moon, and up to two schools can purchase each site. Once the site is registered to the school, they are the only ones besides the scientists with access to Prospector data for that site. The classes voted on whether to get a site on the near or far side, and whether to get a site that had never been explored or one that was shared with another school.

Next the classes researched sites that might show evidence of active volcanism through domes and rilles. They also made a list of sites that had reported TLP activity. Transient Lunar Phenomena are sightings of glows, flashes, shadows or changes on the moon that have been recorded for centuries. Possible sites were checked for availability, then the class voted from a short list of three promising sites.

The site selected is centered at latitude 10 North, 60.85 West, on the near side of the moon. It is located on the Oceanus Procellarum, the Ocean of Storms. This is a mare: an area of younger, dark lava rocks called basalts that cooled about 3 billion years ago. It is not as cratered as the older areas of the Moon, but it does contain a few large craters, the largest of which is Galilaei, with a 15.5 km diameter. It also has a few small domes. The most unusual feature is in its southwest corner - Reiner Gamma.

Reiner Gamma is called an albedo feature. It is near a crustal magnetic anomaly, and one idea is that the magnetic field affects how levitated, charged dust settles, producing an odd, swirly pattern. It also appears to show lunar stratigraphy, composed of thin layers of sedimentary deposits. Reiner Gamma has also been interpreted as a collection of antipodal deposits from extremely large, energetic impacts spreading ejecta clear around the Moon until it implodes together and drops down on the opposite side!

Purpose

The goal of the research was to see if any KREEP or aluminum was on the site, and if it was, to try to correlate it with surface features. KREEP lavas were the last areas of the Moon to be crystallized. Their locations can help in piecing together the history of the Moon, which is poorly understood. KREEP is made of Potassium, Thorium, other rare earth elements and Phosphorus. Aluminum is found mostly in the mineral anorthite in highland areas. The class looked for it on the maria because aluminum may be excavated in bright areas of our site. Underneath those bright areas lie deeper, older rocks areas that could have been brought to the surface by an impact. Also, this resource of aluminum could be used to build aluminum mirrors and make rocket fuel. The Moon could become a primary fuel source for chemical rocketry eventually.

The class also checked for volcanic outgassing events. Two hundred and five data points were sampled to look for traces of gas and the elements described above. The data were downloaded and analyzed at the Moonlink website. They were obtained from two instruments aboard Prospector: the Alpha Particle and Gamma Ray spectrometer.

The Alpha particle spectrometer detects helium nuclei and particles. This could indicate volcanic activity, since such gases would contain helium. This helps determine whether or not the Moon is geologically alive or dead. The gamma ray spectrometer was used to detect the elements of aluminum, thorium and potassium on the Moon’s surface. If thorium and potassium are found together then that means KREEP lavas are present.

Procedure- Alpha Particle Spectrometer Data

The online data lab on the Moonlink site was used to check for alpha particle events. Three data sets at a time were checked. When graphed one would appear in red, one in blue and one in green. The average range in each line would be recorded and then checked for events. Events were anything more than three times the average range. For example, the average on many graphs was one so an event had to be four or above. If an event was found it was listed, noting the date, time, latitude, longitude, range, and height of the event on an Excel chart.

Another control was that events had to be located on the dark side of the Moon, since sunlight striking the surface of the Moon could cause them. They were then checked to see if the events were valid by looking at the cosine angle column in the data. A negative cosine angle meant that the Moon was in darkness when the data were collected. This could be a real event. Although a positive cosine angle could also be real, there was no way to prove that, so all events with positive angles were discarded.

Procedure- Gamma Ray Spectrometer Data

The research group downloaded the actual raw data collected by Lunar Prospector. Next, the online science lab at Moonlink was used. The lab on the website was used to make a graph of each of the data sets summed together and that graph represented the entire data set. The graph across the entire spectrum contains 512 channels. Every element in the graph has a different channel.

The actual value of the data was not necessarily the amount of an element present at the observed location. The actual amount of the element is the value between the plotted continuum and the peak on the graph. The value of the peak was taken from the Moonlink web site and the students checked every data set for the continuum value. It was then possible to compare the two data values and to find the amount of the elements. The main problem with the gamma ray spectrometer is that the data is uncalibrated for concentrations. The actual amount of an element at any given point cannot be determined- it can only be relatively compared within the Moonlink square or between other Moonlink sites.

Another smaller problem is the lack of compensation for altitude. The satellite was orbiting the Moon anywhere between 110 miles and 90 miles away. This difference of 20 miles could result in the satellite picking up a larger area of an element at a lower altitude and a smaller area of an element at a higher altitude. It is comparable to human vision. If something is further away, it will appear to be smaller, and if it is closer, it will appear to be larger, although it never actually changes size.

Data

This is a sample of the gamma ray spectrometer graphs. This particular graph represents the composite of all data. This graph was used to determine ranges and baselines for the individual columns of element data in the spreadsheet.

The data showed that there had been more than forty events. All events had positive cosines, so they were all discarded. Below is a sample graph and a chart showing the information associated with each data file: