Nature of project: experimental, data analysis
Available to students on full-time physics degree schemes or joint students.
Over the last thousand years there have been nearly three thousand reports (mostly through telescopes) of temporary glows, flashes, colourations, and obscurations of detail on the Moon. Unfortunately the Moon is pretty much a geologically dead object and it is difficult to explain phenomena that could occur on, or above the surface that could be seen from the Earth from 400 thousand km away. If we take the solar constant illuminating the Moon to be 1400 W/m^2, and 12% of this gets reflected (by the dark lunar soil) back to Earth i.e. 168 W/m^2, and assume that we can detect >5% variations, then we need some mechanism (if emitted optical radiation is the cause) to radiate ~8 W/m^2 in order to be seen from the Earth on the dayside Moon. On the night side of the Moon, a radiance of just 0.1 W/m^2 would be needed for detections against Earthshine. Of course the effects seen could be due to temporary alterations in the way light is scattered from the surface.
Published theories have included: optical emission and absorption from outgassing, optical scattering from electrostatically levitated dust particles, tribo-electric discharge between electrostatically levitated dust particles in a rarefied gas, optical fluorescence, and impact flashes. Some of these mechanisms in turn may be modulated by passage through the Earths magnetopause and tail, solar flares, solar wind strength, and even Earth-tidal induced deep moon-quakes. Although rare (just a few per year) it is even possible that shallow magnitude 3-5 moon-quakes, could agitate and charge up dust particles initiating some of the dust particle cloud explanations above; shallow Moon quakes, although less powerful than the strongest of Earthquakes, can be sustained for several tens of minutes unlike their counterparts on Earth. More mundane down to Earth explanations have included Rayleigh scattering in our atmosphere making some naturally blue lunar surface features less contrasty to the eye (some observers are more blue/red sensitive than others) at certain times, colour fringing on edges of craters from atmospheric refraction, atmospheric turbulence related effects that let one see tiny pin-point features infrequently thus giving the impression of flashes, and reporting by inexperienced observers.
Even if only a small proprtion of TLP observations are related to processes on the lunar surface, the understanding of TLP will be of special importance when humans eventually return to the Moon. The operation of lunar bases and surface exploration could be severely hampered if these were situated at a site prone to transient out-gassing, or a sink for electrostatic dust deposits. It is interesting to note that gas emission types of TLP may offer a supply of volatiles that could be a useful resource for future colonization of the Moon.
In this project you will attempt to capture evidence of eletrostatic dust particle levitation on the Moon by time lapse imaging of the floors of shadowed craters and the lunar limb region near the poles.
Note that we have archive video data that the students can work with if weather condtions/telescope issues/Covid-19 lock down prevent much in the way of observations.
A successful project will develop beyond the above in one/some of the following directions:
1) Use colour filters to image the interiors of shadowed craters, to see if there is any colour present from wavelength dependent scattering from different size dust particles above the lunar surface.
2) Polarimetry of shadowed areas and the limb, looking for evidence of polarized scattering off dust
3) Organizing amateur astronomers around the world to take images of specific lunar features, at specific solar altitudes for you.
4) Modelling of lunar shadows using LTVT and ALVIS simulation software, and seeing if these can explain past LTP observational reports.
When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.
Additional scope or challenge if taken as a Year-4 project: Obtain diffraction grating spectra of isolated sunlit lunar peaks on the night side of the terminator, especially towards the polar areas where frozen volatiles are known to exist in permanently shadow filled craters.
It could be that meteorite impacts onto the floor of these craters could release volatiles and if seen between us and the illuminated peak, might cause absorption.
It could also be worth checking the spectra of stars that are occulted by the limb of the Moon, near the poles.
Your task will be to investigate these scenarios.
Please speak to Tony Cook if you consider doing this project.
Initial literature for students:
The project is relatively novel as the last thorough review of theories was made in the 1970/80s. Time lapse imaging in narrow wavebands and using the diffraction grating is fairly unique for detecting transient changes on planetary surfaces. Very little assistance will be needed other than discussions with your supervisor and training on the robotic telescopes.
|milestone||to be completed by|
|Robotic telescope training||Christmas|
|Develop software/techniques to look for changes on the Moon in time lapse imagery/video||end of February|
|Analyse captured time lapse imagery for change detection||mid-March|
|Estimate false detection rates caused by image and other forms of noise.||Easter|
Students taking this project will have to submit a full risk assessment form