Posts Tagged ‘meteorite’

Some Thoughts on Transient Lunar Phenomena: 2

July 29, 2017 1 comment

In the previous post of this series, I made the point that Transient Lunar Phenomena (henceforth referred to as TLP) are real and are still poorly understood. I also stated that one type of them, characterized by small flashes lasting for no more than a few seconds, are almost certainly due to meteor strikes on the lunar surface. But what about all those rather infrequent colored mists and luminous discharges that seem to be concentrated in a few locales on the moon?

Well.. after denying their physical existence before the late 1950s, professional astronomers seem to have gradually come to accept them as real. Of course, there are still some credentialed idiots.. I mean astronomers who love to create every elaborate explanations about how they are an artifact of observation. But enough about those worthless hucksters. Anyway, we are still stuck with trying to understand what process causes them in the first place.

To date, four explanations are usually offered to explain TLPs. Two of them, namely ‘Impact Events’ and ‘Unfavourable Observation Conditions’ have already been discussed with the prior being true for one category of TLPs and the later being an excuse for elaborate hand-waving by sophists. And this leaves us with the other two explanations: ‘Outgassing’ and ‘Electrostatic Phenomena’. While both are feasible and not as mutually exclusive as you might think, they still do not answer the central question- what are we observing in the first place?

The most poorly answered question about TLPs which last for more than a few seconds has always been- “what is the chemical composition of whatever is being observed?”. The simple answer to that question is that we either don’t know for sure or have mutually contradictory data. But why? How come we have tons of data about composition of the atmosphere of Venus, Mars, moons like Titan and other planets but very little information about temporary changes in the chemical composition on the lunar surface that accompany TLPs.

It comes down to two factors:

(1) Almost all studies on the chemical composition of non-terrestrial bodies is done by using some forms of spectroscopy. In other words, measurements of the chemical composition of non-terrestrial bodies are almost all indirect measurements of how photons of some wavelength interact with atoms (or molecules) of whatever is being studies. A secondary effect of being reliant on spectroscopy for such studies is that the equipment to do that is far scarcer than for simple observation of those bodies at optical or near-optical wavelengths.

(2) A lot of the scientific interest and funding for studying the moon disappeared after the late 1960s.Today, there are very few financial and instrumental resources for studying phenomena on the moon, especially one as ephemeral as TLPs. I should also point out that TLPs, while vaguely accepted by the professional astronomical community, are still not seen as “respectable” research especially in a world where scientific research has become another extension of neoliberal ideology- with an emphasis on “productivity”, “metrics” and being non-offensive to “authority”.

But we still have not touched what I believe is the central question about TLPS, namely what are they made of- chemically speaking? Or perhaps a better way to phrase that question is- what would be the likely chemical constituents of TLPs?

Before we tackle that question, let us reacquaint ourselves with some basic facts about conditions at the lunar surface and the moon in general. Firstly, the moon has basically no atmosphere worth mentioning and therefore any gaseous emissions from the interior of the moon will quickly dissipate into the near vacuum which prevails near its surface. Contrast that to earth where, for example, the gas and dust from a volcanic eruption will hang around for days. Secondly, the lunar surface has not witnessed extensive volcanism for at least a billion years. There is however evidence that minor volcanic eruptions on the moon have occurred as recently as 50-100 million years ago.

Thirdly, the moon is substantially smaller than the earth and contains a far smaller metallic core. The point I am trying to make is the moon should be geologically far more deader than it is in reality. Then again, that is what most people used to believe about Pluto and Ceres till space-probes visited them in the previous 2-3 years. To put it another way, a lot of what astronomers thought they knew about factors responsible for geological activity on non-stellar celestial bodies is, at best, incomplete. And this brings us to the issue of what we know about the composition of gaseous emissions from the moon.

One of the first spectrograms of such an event, in 1958, suggested the presence of something containing carbon in the emissions. Observations by manned and unmanned spacecraft have also shown that some regions of the moon give of far more Radon-222 than others. Curiously enough, these areas of the moon happen to be TLP hotspots. To make a long story short, the idea that some regions of the moon often release small amounts of gases is now largely accepted. So far so good.

But here comes the curveball.. all gases known to emanate from the lunar surface (nitrogen, argon, radon, helium, methane?) are colorless! As you might recall, TLPs were first noticed because of changes in luminosity and color in regions with a size of least 3-4 square km. Which means that whatever is released during these events is either one (or more) colored gasses or some form of dust with a particle size that gives it some color when exposed to sunlight. On earth, most of the color in the smoke of volcanic emanations is caused by various compounds of sulfur or nitrogen and basalt dust which absorb light of a higher wavelength than orange.

Given that the laws of physics are constant throughout the universe and chemical composition of the moon is unlikely to be radically different from Earth- it stands to reason that the colors and luminosity changes seen during TLPs are due to the release of emanations with more than a passing similarity to those from some volcanoes on earth. Yet, there is no evidence for currently active volcanoes (as we would define them) on the moon- even though we know the location of more than a few extinct ones. The lunar surface also has atypical and small volcanoes.

TLPs, in my opinion, are due to the release of gaseous compounds (including those of sulfur and nitrogen) and basaltic dust by volcanic features similar to Fumaroles and Fissure Vents on Earth. Their distribution on the moon might be linked to the distribution of especially thin and fractured lunar crust. Of course, accepting such a hypothesis would mean that a lot of what we have believe about the internal geology of moon and other celestial bodies of similar sizes is rather incomplete- to say the least. Then again, we could always preserve existing dogma by ignoring such phenomena or pretending that it not real.

What do you think? comments?

Some Thoughts on Transient Lunar Phenomena: 1

July 24, 2017 2 comments

As a few of you might know, I have always had a strong interesting in astronomy and related areas of the sciences. In fact, many years ago, I seriously considered a career in astrophysics or something along those lines. In the end, I chose an area of research which was more likely to result in a well paid job. Anyway, the point I am trying to make is that I always had a strong interest in, and considerable knowledge of, areas of science that concern the study of celestial objects- which also explains why I have a much better than average understanding of rocketry, among other things.

But what does any of this have to do with my thoughts on transient lunar phenomena?

Well.. a lot. One of the reasons I became interested in astronomy, you see, was my interest in the moon. While people had visited the moon many years before I was born, it still remains the easiest celestial object to study. This is especially so if you grew up in a semi-urban area with moderate light pollution. While where I grew up was dark enough to catch a glimpse of many objects in the Messier and Herschel 400 List, there were times when I ended up watching the moon for hours at a time- usually waiting for some deep sky object to reach a decent elevation above the horizon.

This brings me the subject of what I was watching on the moon. While the moon has been well-studied and documented for decades, and even before manned exploration, there are many reasons why amateur astronomers still study it. For one, there is a certain thrill to being able to see, with your own eyes, craters as small as a few kilometers across (4-5 km) on something about 0.4 million km away. The limits to what you see on the moon (in terms of size) depends on the aperture of your instrument (Dawe’s limit), location on the moon and lighting conditions.

Then there is the tiny chance that you will witness an example of what is popularly known as transient lunar phenomenon aka TLP. To be fair, TLPs are a bit like the lunar version of UFOs, in that they were for a long time considered to be observational artifacts- otherwise known as people seeing things. And why not.. over the last hundred years, scientists have been almost unanimous that the moon has been geologically dead for a very long time- like a couple billion years, at least. Moreover many moon rocks collected by astronauts in late 1960s and early 1970s appear to be 3 to 4 billion years old.

But before we go further, let us talk about the two major types of TLPs. The first type, which last less than a few seconds and are not controversial involve the effect of meteors (meteorites) impacts on the moon. It is not unheard of, especially if you have a decent sized telescope and lots of time or a continuous CCD recording to occasionally see very tiny flashes of light on the unlit parts of the moon. Over a period of many years and hundreds of hours of observation with a 8-inch aperture telescope, I am reasonably sure that I have seen a few tiny flashes, especially when I was looking at the edge of the lit and unlit regions of the moon.

An early and fortuitous photo of what appears to be a meteorite impact on the moon was taken in 1953 by an amateur astronomer named Dr. Leon H. Stuart. Since then, others have taken many more photos and videos of similar (but much fainter) events on the moon. Basically, any meteorite with a mass between several tens to several hundreds of kilograms hitting the lunar surface can produce enough light to be picked up CCD devices attached to telescopes with an aperture larger than 12 inches (or 300 mm)- if they happen to be looking at the right area. The event Leon Stuart photographed was however likely caused by a much larger meteorite- probably one weighing several tons, if not more.

The second type of TLPs, which are far more controversial and rarer, appear as highly localized and often colored mists frequently accompanied by temporary brightening or darkening of the surrounding area. These events usually last for somewhere between a few minutes to a few hours. Also, they seem to occur far more frequently near certain craters and features on the lunar surface than would otherwise be the case. An example of this second type of TLP photographed by Audouin Dollfus in 1992 can be seen below. Over the decades, more than a few astronomers have reordered such localized and transient changes on the lunar surface- both in photographs as well as other light-based measurements.

So what is going on? Is it evidence of volcanic activity? Or outgassing? or some weird electrostatic phenomenon? could it be all due to unfavorable observation conditions? or something else? My personal favorite explanation for the second types of TLPs involves a version of the outgassing hypothesis. However, as you will in the upcoming part of this short series, it is somewhat different from the most common version of that explanation- and I will go into some detail about my reasoning for choosing that particular one over others.

What do you think? Comments?