STRANGE LIGHTS ON THE MOON ------------------------ John Pazmino NYSkies Astronomy Inc www.nyskies.org email@example.com 2007 October 23
Introduction ---------- Dr Arlin Crotts, Columbia University, heads up a project to collect new consistent data about the transient luminous phaenomena occasionally reported on the Moon. he gave several talks about this work in summer and fall 2007, including one to NYSkies on September 6 and to he Columbia outreach program on October 19. This summary blends the Columbia and NYSkies presentations, they being similar with substantial overlap.
Origin of the Moon ---------------- Crotts explained the current scenario for the origin of the Moon. In the nascent era of the solar system, a coorbiting protoplanet about 1/10 Earth mass wandered too close to earth and collided with it. The impact tore off part of the crust and mantle, which with the material of the colliding planet, consolidated into the Moon. In many descriptions of this episode, the collider is described as 'Mars size' or 'the size of Mars'. While Mars is about 1/10th Earth mass, it is far too easy to lose the comparative sense of the words and recall that 'Mars collided with Earth'. There is no evidence of any kind that Mars ws any where close to Earth for such a collision. The removal of crust from earth in the collision left Earth with a thin residual layer of only several kilometers depth. In contrast, venus has a crust about 50 kilometers thick, plausibly because it never suffered a major accident like Earth. If the material of the Moon is spread out over Earth, it would form a layer about 50 kilometers deep. This seems to support that thought that the Mon is made of material broken from Earth.
Cratering ------- Both Earth and Moon, and most other solid-crust bodies in the solar system, suffered a massive bombardment of large bodies. These impacts formed the craters on the Moon in numbers seemingly without limit. The earlier impacts were from larger bodies, the sizes tapering off in later eras. That's why in so many cases, crates overlap in size hierarchy from larger under smaller. For the most part, the lunar craters are collisional relics, but some of them triggered internal lava flows to form the maria and fill in certain craters. It is still not certain why only 20ish percent of the Moon has the maria, just about all on the near side. The far side is almost entirely bashed up with craters. The Moon endures meteor flux today under a constant rain of small stones, of the kind that cause meteors on Earth. The impact speed is centered on the escape velocity of the Moon, 2Km/s. Hence, even a pebble can cause major damage to a fragile structure like a habitat. With no atmosphere to burn them up, all approaching material hits the surface. Earth, too, undergoed this same severe bombardment. With its stronger gravity, the results may have been worse than on the Moon. However, Earth hs tectonics, volcanism, weathering, water erosion. Virtually all of the craters are oblitterated such that we have only a couple hundred of them left.
Quiet era ------- After the initial formation and cratering, the Moon (and Earth) were freed of most space-based influences. The flux of solar radiation continues, tempered on Earth by the atmosphere. But there are essentially no new large craters. A few recent ones, tens to hundreds of millions of years old, still display splash marks, the rays. The Moon is too small to have plate structure to modify the surface, not enough internal hat to sustain substantial volcanos, no atmosphere or water for weathering and erosion. The Moon today is about as it was 3-1/2 billion years ago. One reason for the Apollo and possible future return lunar visits is to study the conditions of that time as clues to the early history of the solar system. The only new large craters on the Moon are those made by the deliberate crashing of used up Apollo rockets. These were part of experiments to hit the Moon with known mass and speeds to observe the seismic reaction. On earth this record is mostly gone by the movement and mutation and destruction of very old materials.
Lunar exploration --------------- Until the space age the Moon was examined only from the ground with a best resolution of a half kilometers by eye and one kilometer by conventional photography. Earth atmospheric turbulence prevented better detail from being recorded. The prevailing rhetoric was that the Moon was a dead world with no changes occurring there. Visits to the Moon began in the late 1950s by USSR Lunik craft. They flew by the Moon, capturing photographs of the surface close up and on the far side. Landings started in the 1960s with the US Surveyor and Apollo craft. These examined the 'terrain' and brought back soil and rock samples. Both US and USSR continued lunar explorations thru the mid 1970s. Only the US fielded human crews while USSR collected samples by robot visits. Then the Moon was meglected! It wasn't until the mid 1990s that Celmentine and Prospector went for orbital mapping and inspection. Now, in the 20-thous, there is an upsurge in lunar visits by many countries. Among them are japan, China, ESA, as well as US and Russia. *The Soviet Union died in about 1992.)
Strange lights on the Moon ------------------------ On and off in the 18th thru mid 20th century, astronomers reported lights, flashes, clouds, mists on the Moon. These reports were haphazardly recorded and could be mistakes of interpretation. Others seem pretty secure witness of real events. There was no organized way to record these lights, nor any unified way to report them. They ended up in newsletters and magazines, often now hard to obtain. With the singular exception of the famous flashes in crater Alphonsus in the mid 1950s, just about all reports were accidental notices from home astronomers. The Alphonsus event was recorded by the Soviets, making it at first a work of propaganda or disinformation in the Cold War. In time it was appreciated for a real occurrence. But that was about it
Crotts's work ----------- Dr Crotts wants to gt a handle on the objective behavior of the Moon, partly as preparation for human visits in the next decade. He studied the extant litterature and found that most events were too loosely recorded. However, he tried to rework the reports into a useful database. He found that over the centuries only two places on the Moon consistently exhibit strange lights. These are the area around crater Aristarchus and within crater Plato. Other regions have too few reports to count as 'regular' hot spots. One area Crotts found too inconsistently reported is Mare Crisium. He believes the events there may be misinterpretations of light & shadow. Plotting the events on a lunar map reveal that they all sit near the shores of the larger maria or in the plateau of Aristarchus. Thus, to a minor extent, the Moon has its own 'ring of fire' with a 'Hawaii' in the middle!
Atmosphere -------- The Moon has no substantial atmosphere. The total mass of all the retained gases over the entire lunar globe is, uh, about 20 tons. 20,000 kilograms. This is but half the mass of a single NYC subway car! This atmosphere is made of argon, helium, radon, all from internal radioactive decay in the lunar interior. Thee is also a mix of 'organic' gases, including water vapor!, in trace amounts. These Crotts thinks come from comet detritus. Despite the low gravity, a gas locally released into the 'air' will not instantly fly away. It'll linger in place, there being no wind or other means of dissipating it, for hundreds of years. As the random molecular motions excede escape velocity in the upward direction, the gas will in time leak off. Crotts explained there are two atmospheres. One made from neutral atoms; the other, ionized ones. The neutral atoms stir up in the lunar daytime and loft higher above the ground. This is most severe at the sunrise terminator. At night the atoms cool and settle closer to the ground. Other wise they don't move around much. The ions also heave and sigh with diurnal temperature change, but also are driven around the Moon by solar induced magnetic fields. With the minuscule number of air atoms to start with, about 1,000 per cubic meter[!], such ion migration causes no effect on the lunar landscape.
Surface ----- The lunar soil and rocks, bought back by the US and USSR probes, have about the same isotope mix as on Earth. Crotts noted that this mix varied with remoteness from the Sun, such that meteorites from the asteroid belt or the outer solar system have different isotope ratios. This consistency of ratio supports the local origin of the Moon, possibly by the collision hypothesis. However, the 'soil' is not at all like earth's. It is entirely of mineral composition like sand or pulverized rock, with no organic content at all. The particles are gritty and abrasive, as confirmed by damage to Apollo apparatus. It also contains large amounts of vitreous beads of submillimeter diameter. This compositions is consistent with a melted condition in the Moon's early age. The soil is several meters thick, and churned over by pelting from solar wind, cosmic rays, and small meteors. Under this top layer is the solid crust, often of basalt or lava. The gases released into the 'air' likely come from pockets cracked when the maria formed but are trapped under the many meter thick crust. It doesn't take much tectonic or geologic force to burst thru the crust and cause an eruption. These are rare but possible along the marial shores. Such eruptions are likely the lights, mists, &c seen over the years. At lest, while a specific event can not be verified, the overall behavior of the events globally is feasible.
Aristarchus --------- The crater Aristarchus is a new crater, perhaps 80 million years old. It is filled with brilliant reflective material that makes it the brightest spot on the Moon's near side. It isn't yet covered by fresh dust and silt or discolored by solar radiation. These factors temper the bright splashes of older craters and erased those of the oldest craters. It sits on a high mesa some 250 meters above the surrounding mare floor. This mesa covers Aristarchus, nearby HErodotus, and the Schroeter Valley. Other smaller valleys crisscross this region. The fractured terrain could be outlets for frequent gas eruptions. As the gases escape they could be ionized by solar radiation, then recombine to emit the various glows noted in the historical records. One heartbreak, that delayed the solution of the strange lights problem, is the cancellation of lunar visits after Apollo 17. Apollo 18 was targeted for the Aristarchus plateau prima mente to study outgassing there!
New observatories --------------- Crotts and his team are building small remote telescopes to continuously watch the Moon. Built from stock equipment of home astronomy specifications, they are tested on the roof of Pupin Hall at Columbia, in Morningside Heights, Manhattan. The use of home astronomy equipment is an other example of how it in the past ten years improved in capability and competence, yet decreased in real dollar cost. The first is at Cerro Tololo Interamerican Observatory, Chile. The second is in western Australia. A third, under construction, will be sited in western Russia. The three sites span enough longitude to see the Moon whenever it is in the local night sky for most of the 24 hour diurnal cycle. CCDgrams will ba captured every couple seconds and correlated by computer analysis to spot sudden brief changes. The images are full disc frames with 1Km resolution. as good as the Earth atmosphere allows with rigid optics. Simultaneous images from two scopes will eliminate line-of-sigh meteors, CCD flaws, cosmic ray hits, and other local noise. It is plausible that some of the flashes seen on the Moon will be actual meteor crashes, as tracked by Bill Cooke at Marshall Space Flight Center.
Spaceprobes --------- A day or two before Crotts's Columbia talk the Japan lunar craft SELENE settled into its orbit and was returning working data. One instrument is a radon detector. Crotts will compare his pictures of lunar lights with the sites at which SELENE spotted excess radon. The match will strengthen the outgassing theory. Such comparison could not be made with earlier radon sensors because there was no coordinated monitoring of lunar lights. The Apollo landers had such devices. They recorded radon outbursts until they died or were turned off. The landing sites hundreds of kilometers from suspected hotspots and understanding was too poor of the lunar ion migration to track the gasses back to them.
Major concern ----------- Arlin Crotts is worried that with the many human flights to the Moon by 2020 thee may be irreversible destruction of the lunar atmosphere. Each human mission will exhaust on or near the Moon many tons of rocket gases. That's a huge fraction of the native air! In a few visits, the Moon could end up with an atmosphere predominately human-made!! Hence, it is crucial to do the lunar lights study NOW, as well as other studies of the pure lunar environment, BEFORE human 'footprints' wipe out the eons-old record.