Transient Lunar Phenomena: Mysterious Flashes on the Moon
For centuries, astronomers have been puzzled by mysterious bright flashes that can occasionally be seen on the surface of the moon. Recorded sightings of these flashes date back to the 6th Century, and they have been seen by casual observers, dedicated astronomers, and Apollo astronauts in lunar orbit.
There have been a number of potential causes suggested for these Transient Lunar Phenomena, or TLPs - meteorite impacts, outgassing, moonquakes, and electrostatic phenomena. Other studies have questioned the existence of these phenomena, suggesting that they are likely caused by reflections from Earth-orbiting satellites, atmospheric interference, or are simply a result of observer error.
A new paper by a group of French astrophysicists provides some strong evidence that meteorites are indeed the cause of these fascinating phenomena. According to lead author Sylvain Bouley of the Institut de Mécanique Céleste et de Calcul des Ephémérides in Paris, a meteorite as small as 10 centimeters in diameter could produce a flash visible from Earth.
The authors of the paper, which will appear in the March 2012 issue of the journal Icarus, analyzed video recordings of TLPs made between 1999 and 2007. They noted the duration, intensity, and likely origin of the meteorites - known meteor showers versus sporadic events - and used this in conjunction with known models of black-body radiation to calculate the total radiated energy from the events.
The flashes, they concluded, are likely the result of superheated melt droplets kicked up by high-speed impacts. As these droplets cool, their energy is radiated into space as visible light, producing the transient lunar phenomena observed from Earth.
"Hey, Houston. I'm looking north up toward Aristarchus now, and I can't really tell at that distance whether I am really looking at Aristarchus, but there's an area that is considerably more illuminated than the surrounding area. It just has—seems to have a slight amount of fluorescence to it."
- Michael Collins
Apollo 11 Command Module Pilot
July 19, 1969, 6:44 p.m. UTC
Case Closed... Or Is It?
A prior study by Columbia University astronomy professor Arlin Crotts found strong correlations between TLPs and detected releases of Radon-222 gas on the Moon. The distribution of these lunar phenomena on the Moon's surface also shows a strong correlation with the boundary regions between mare regions and the lunar highlands.
In this study, transient lunar phenomena also appeared to be centered around significant impact craters, particularly the Plato crater on the northeastern shore of the Mare Imbrium and the prominent Aristarchus crater on the northeast portion of the Moon's near side. In 1969, an event was observed in the Aristarchus crater by German astronomers, then confirmed visually by the Apollo 11 astronauts while in lunar orbit.
The Crotts study suggested that the primary origin of these flashes may not be meteorites, but outgassing resulting from landslides of geologically-recent crater material, and ongoing lunar tectonic activity that has been detected by seismometers left on the Moon by the Apollo missions.
Both studies concluded that more data and better observing techniques were needed to fully address the outstanding questions in these still-mysterious flashes. Though these recent findings provide some interesting clues, it appears that this mystery may not be solved any time soon.
Sources and More Information
- Power and duration of impact flashes on the Moon: Implication for the cause of radiation
Bouley, S. et al. Icarus. Volume 218, Issue 1, March 2012, Pages 115–124
- Molten Blobs Create Moon Flashes - Science News
Mysterious lunar lights are the superhot remains of meteorites pelting the surface
- Mystery Moon Flashes Caused by Meteorite Impacts
For hundreds of years, people have seen tiny flashes of light on the surface of the Moon. Very brief, but bright enough to be seen from Earth, these odd flashes still hadn’t been adequately explained up until now. Also known
- Lunar Outgassing, Transient Phenomena, and the Return to the Moon. I. Existing Data
Transient lunar phenomena (TLPs) have been reported for centuries, but their nature is largely unsettled and remains controversial.
- NASA - Lunar Impact Monitoring News
Marshall Space Flight Center: NASA's Lunar Impact Monitoring index page