http://www.physorg.com/news102175962.html
Astronomer Offers New Theory Into 400-year-old Lunar Mystery
Image of TLP taken in 1953, courtesy of Columbia’s Department of Astronomy. The TLP is the small, bright spot in the center of the image. Credit: Columbia University
Columbia astronomy professor Arlin Crotts thinks he has solved a 400-year-old mystery: the origin of strange optical flashes often reported as appearing on the moon’s surface.
Transient Lunar Phenomena (TLPs), in which the lunar surface reportedly changes in brightness, blurriness or color, have been photographed and observed by thousands of astronomers over the centuries. Yet explanations of why they occur and even their reality as true lunar phenomena have been hotly debated. The TLPs typically cover a space of a few kilometers and last for several minutes.
Crotts has uncovered a strong statistical relationship between TLPs and so-called outgassing events on the lunar surface. Outgassing occurs when gases trapped beneath a moon or planet are released and, if only briefly, become part of the object’s atmosphere. A key component of this gas is radon.
“People over the years have attributed TLPs to all sorts of effects: turbulence in Earth’s atmosphere, visual physiological effects, atmospheric smearing of light like a prism, and even psychological effects like hysteria or planted suggestion” says Crotts, “but TLPs correlate strongly with radon gas leaking from the moon. No earth-bound effect can fake that.”
To arrive at his theory, Crotts correlated TLPs with known gas outbursts from the lunar surface as seen by several spacecraft, particularly NASA’s Apollo 15 mission in 1971 and the robotic Lunar Prospector in 1998. What he discovered was a remarkable similarity in the pattern of outgassing event locations recorded by spacecraft across the face of the moon and reported TLP sites.
The pattern was further strengthened after Crotts performed a statistical test to rid the sample list of false reports and one time events that might not represent true outgassing sources. “The result,” says Crotts “shows that some lunar event sites that were the focus of great observer excitement over recent decades disappeared from the more highly refined list of TLP sites.” Crotts used two catalogs of such sightings amassed and edited three decades ago by now retired astronomers Barbara Middlehurst and Winifred Cameron.
Crotts says this research might lead to optical imaging of the lunar surface that could monitor how, when and where gas escapes from the moon. While the exact composition of this gas is largely unknown, he explains, hints from previous measurements indicate that it might contain substances beneficial for future moon explorations, especially water.
Until now, Crotts says two factors have worked against researchers solving the mystery of TLPs. Historically, outgassing has often been discussed by scientists, but many have considered the moon volcanically dead despite moonquakes and episodes of gas, such as argon, observed coming from the lunar surface. Another deterrent to researchers is the daunting volume of visual data associated with TLPs – a fact that plays to Crotts’ particular research interest and skills.
Along with collaborators Professors Paul Hickson from the University of British Columbia, and Thomas Pfrommer and Cameron Hummels of Columbia, Crotts recently built the robotic camera at Cerro Tololo Inter-American Observatory in northern Chile. It will automatically scan the moon for TLPs every few seconds and produce an unbiased map of the distribution, free of potentially flawed sightings due to human error, poor equipment, or improperly recorded observations that have dominated TLP studies until now. The scientists are planning even more monitors and hope they will establish with much greater accuracy the exact locations of gas leaks on the moon.
Crotts says improved TLP maps are already pointing to intriguing features on the lunar surface, and he is currently preparing a separate article on that subject.
Source: by David Poratta, Columbia University
Transient Lunar Phenomena: Regularity and Reality
Authors: Arlin P.S. Crotts
(Submitted on 27 Jun 2007)
Abstract: Transient lunar phenomena (TLPs) have been reported for centuries, but their nature is largely unsettled. A review of TLP reports shows regularities in the observations; a key question is whether this structure is imposed by human observer effects, terrestrial atmospheric effects or processes tied to the lunar surface. I interrogate an extensive TLP catalog to determine if human factors determine the distribution of TLP reports. I divide the sample according to variables which should produce varying results if determining factors involve humans e.g., historical epoch or geographical location of the observer, not reflecting phenomena tied to the lunar surface. Regardless of how we split the ample, the results are similar: ~50% of the reports involve crater Aristarchus nd vicinity, ~16% from Plato, ~6% from other recent, major impacts, plus a few at Grimaldi. Mare Crisium produces a robust signal for three of five averages of up to 7% of the reports (however, Crisium is an extended feature). The consistency in TLP report counts for specific features indicates that greater than ~80% of reports are consistent with being real (perhaps excepting Crisium). Some commonly reported sites disappear from the robust averages, including Alphonsus, Ross D and Gassendi. TLP reports supporting these sites originate almost entirely after year 1955, when TLPs became more popular targets of observation and many more (and inexperienced) observers searched for TLPs. In a companion paper, we compare the spatial distribution of robust TLP sites of transient outgassing (seen on Apollo and Lunar Prospector). To a high confidence against the random hypothesis, robust TLP sites and those of lunar outgassing correlate strongly, further arguing for the reality of TLPs. [Abstract abridged.]
Comments: 45 pages, 1 figure, submitted to ApJ. Other papers in series found at this http URL
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0706.3947v1 [astro-ph]
Submission history
From: Arlin Crotts [view email]
[v1] Wed, 27 Jun 2007 03:20:38 GMT (330kb)
http://arxiv.org/abs/0706.3947
Lunar Outgassing, Transient Phenomena and The Return to The Moon, I: Existing Data
Authors: Arlin P.S. Crotts
(Submitted on 27 Jun 2007)
Abstract: Herein the transient lunar phenomena (TLP) report database is subjected to a discriminating statistical filter robust against sites of spurious reports, and produces a restricted sample that may be largely reliable. This subset is highly correlated geographically with the catalog of outgassing events seen by the Apollo 15, 16 and Lunar Prospector alpha-particle spectrometers for episodic Rn-222 gas release. Both this robust TLP sample and even the larger, unfiltered sample are highly correlated with the boundary between mare and highlands, as are both deep and shallow moonquakes, as well as Po-210, a long-lived product of Rn-222 decay and a further tracer of outgassing. This offers another significant correlation relating TLPs and outgassing, and may tie some of this activity to sagging mare basalt plains (perhaps mascons). Additionally, low-level but likely significant TLP activity is connected to recent, major impact craters (while moonquakes are not), which may indicate the effects of cracks caused by the impacts, or perhaps avalanches, allowing release of gas. The majority of TLP (and Rn-222) activity, however, is confined to one site that produced much of the basalt in the Procellarum Terrane, and it seems plausible that this TLP activity may be tied to residual outgassing from the formerly largest volcanic ffusion sites from the deep lunar interior. With the coming in the next few years of robotic spacecraft followed by human exploration, the study of TLPs and outgassing is both promising and imperiled. We will have an unprecedented pportunity to study lunar outgassing, but will also deal with a greater burden of anthropogenic lunar gas than ever produced. There is a pressing need to study lunar atmosphere and its sources while still pristine. [Abstract abridged.]
Comments: 35 pages, 3 figures, submitted to Icarus. Other papers in series found at this http URL
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0706.3949v1 [astro-ph]
Submission history
From: Arlin Crotts [view email]
[v1] Wed, 27 Jun 2007 03:34:43 GMT (572kb)
http://arxiv.org/abs/0706.3949
Lunar Outgassing, Transient Phenomena and The Return to The Moon, II: Predictions for Interactions between Outgassing and Regolith
Authors: Arlin P.S. Crotts, Cameron Hummels
(Submitted on 27 Jun 2007)
Abstract: We consider the implications from Paper I on how gas leaking through the lunar surface might interact with the regolith, and in what respects this might affect or cause the appearance of optical Transient Lunar Phenomena (TLPs). We consider briefly a range of phenomena, but concentrate at the extremes of high and low gas flow rate, which might represent the more likely behaviors. Extremely fast i.e., explosive, expulsion of gas from the surface is investigated by examining the minimal amount of gas needed to displace a plug of regolith above a site of gaseous overpressure at the regolith’s base. The area and timescale of this disturbance, it is consistent with observed TLPs. Furthermore there are several ways in which such an explosion might be expected to change the lunar surface appearance in a way consistent with many TLPs, including production of obscuration, brightening and color changes. At the slow end of the volatile flow range, gas seeping from the interior is retained below the surface for extensive times due to the low diffusivity of regolith material. A special circumstance arises if the volatile flow contains water vapor, because water is uniquely capable of freezing as it passes from the base to the surface of the regolith. For a large TLP site, it is plausible to think of areas on the square-km scale accumulating significant bodies of water ice. Furthermore, as the system evolves over geological time, the ice accumulation zone will evolve downwards into the regolith. Since many reactions possible between the volatiles and regolith, depending on the additional gases besides water, can act to decrease diffusivity in the regolith, it is plausible that the volatiles produce a barrier between the seepage source and vacuum, forcing the ice zone to expand to larger areas.
Comments: 23 pages, 2 figures, submitted to ApJ. Other papers in series found at this http URL
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0706.3952v1 [astro-ph]
Submission history
From: Arlin Crotts [view email]
[v1] Wed, 27 Jun 2007 03:48:47 GMT (51kb)
http://arxiv.org/abs/0706.3952
Lunar Outgassing, Transient Phenomena and The Return to The Moon, III: Observational and Experimental Techniques
Authors: Arlin P.S. Crotts
(Submitted on 27 Jun 2007)
Abstract: In Papers II and III we show that Transient Lunar Phenomena (TLPs) are likely related to lunar outgassing, albeit in ways not fully understood. Here we propose a path forward, in which current and forthcoming technologies provide a more controlled, sensitive probe of lunar outgassing. Many of these techniques are being realized for the first time. Given the optical transient/outgassing connection, progress can be made by remote sensing, and we suggest programs of imaging, spectroscopy and combinations thereof. However, as found in Paper II, many aspects of lunar outgassing seem covert in nature. TLPs betray outgassing, but not all outgassing produces TLPs. Some outgassing may never appear at the surface, but remain trapped in the regolith. We also suggest more intrusive techniques, from radar mapping to in-situ probes. Understanding these volatiles seems promising in terms of a resource for humans on the Moon and beyond, and offers an interesting scientific goal in its own right. Hence this paper is a series of proposed techniques, some in practice, some which might be soon, and some requiring significant future investment, some of which may prove unwise pending results from predecessor investigations. These point towards enhancement of our knowledge of lunar outgassing, its relation to other lunar processes, and an increase in our understanding of how volatiles are involved in the evolution of the Moon. We emphasize certain ground-based observations in time for flights of SELENE, LRO and other robotic missions, and others before extensive human xploration. We discuss how study of the pristine lunar atmosphere pertains to understanding the role of anthropogenic volatiles, an important confusing signal
Comments: 33 pages, 4 figures, submitted to ApJ. Figures 5-6 and other papers in series found at this http URL
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0706.3954v1 [astro-ph]
Submission history
From: Arlin Crotts [view email]
[v1] Wed, 27 Jun 2007 04:20:31 GMT (814kb)
http://arxiv.org/abs/0706.3954
Transient Lunar Phenomena - TLP
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