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Of Telescopes on the Moon

Putting an enormous radio telescope on the far side of the Moon has so many advantages that it’s hard to imagine not doing it, once our technology makes such ventures possible. Whatever the time frame, imagine an attentuation of radio noise from Earth many orders of magnitude over what is possible anywhere on the near side, much less on Earth itself. In a recent telephone conversation, I discussed these matters with Italian space scientist Claudio Maccone, whose work on a mission to the Sun’s gravity focus we’ve examined in these pages before.

Having just completed a week at Rutgers attending its Symposium on Lunar Settlements, Maccone anticipates the publication of his new paper on the lunar far side and its scientific potential — I’ll have to put off the specifics of those interesting ideas until the paper actually appears. But do ponder the implications of a radio observatory conceivably able to probe extrasolar planets. As a news item in New Scientist explains:

The interaction of charged particles such as electrons with the magnetic fields of extrasolar planets should produce low-frequency radio waves. They could provide information on the interiors of extrasolar planets, as the internal structure and composition governs the strength of the magnetic field.

How to build such an array and, even more to the point, just where to put it is a subject we’ll take up soon in relation to Maccone’s work. But with science on the Moon’s surface in mind, the news of what appears to be a breakthrough in liquid mirror technology for use in an entirely different kind of telescope catches the eye. Ermanno Borra (Laval University, Quebec) and team seem to have conquered the temperature problem, allowing the possibility of building telescopes with large, liquid apertures on the lunar surface.

Setting up a rotating frame containing liquid mercury is a proven technique for constructing high-precision mirror-like surfaces, but at lunar temperatures, the substance freezes. Borra’s group uses complex salts in the form of so-called ‘ionic liquids’ whose freezing point is below ambient lunar temperatures. A fine layer of chromium particles is deposited on the liquid followed by a layer of silver particles. Here we’re talking not radio telescopes, as in Maccone’s work, but an optical and infrared instrument, and one of fantastic precision compared with what is available today.

A quick look at the team’s recent paper reveals the concept: an optical instrument with infrared capabilities with an aperture up to 100 meters in size. That allows observations of objects anywhere from 100 to 1000 times fainter than what the James Webb Space Telescope will see. Pete Worden, director of NASA Ames and a co-author of the paper, says of the concept, “In this case we have shown how the moon is ideal (for) using liquid mirror technology to build a telescope much larger than we can affordably build in space.”

The paper is Borra et al., “Deposition of metal films on an ionic liquid as a basis for a lunar telescope,” Nature 447, 979-981 (21 June 2007), abstract available. A New Scientist story on Borra’s work is also available. It should be noted that this is yet another project funded by NASA’s Institute for Advanced Concepts, whose record at advancing cutting-edge ideas like this from raw speculation into the realm of proven laboratory work is well established. Without NIAC, how will the next generation of advanced concepts gain financial traction?

Comments on this entry are closed.

  • Darnell Clayton June 25, 2007, 11:06

    I first heard about this idea and originally wrote this off due to the fact that the moon isn’t always warm on the surface (especially in the shadows) thus resulting in the mercury freezing up.

    Now that someone has conquered this, the idea of a liquid telescope looks to be feasible.

    Question: Now that freezing has been addressed, what about the liquids getting so hot that they boil away? Will the mercury mixture be protected, and if not, will the other “mixtures” evaporate, leaving the mercury at the mercy of the freezing lunar shadows?

  • David June 25, 2007, 12:01

    Interesting, one big problem not mentioned though is
    how to deal with the lunar dust. The Apollo astronauts found that no matter how careful one was, the dust went everywhere. Having dust on the mirror or the hardware is not what one wants. I imagine it would be particularly a problem during construction.

  • f June 25, 2007, 13:10

    Darnell: the telescope would be built inside a crater, in a place where it would never be illuminated by the Sun, and thus never turn hot. The real challenge though is dealing with vacuum. If you somehow manage to keep the mercury liquid (instead of freezing) (and that is one trick, that the article is about), then it should easily evaporate under “zero atmospheric pressure”. The article mentioned deals with that too.

    David: probably they will have to design a very careful, automated way of automatically uncover the mirror surface and pour in the mercury, by some sort of robot. If they set this up, people leave and turn on the unwrapping and pouring robot, and never again enter the vicinity of the whole thing, then maybe it would be free of dust.

    But maybe you would need to service the telescope at times. Doesn’t sound easy…

  • Administrator June 25, 2007, 13:35

    The dust problem sounds like one of those ‘small problems of engineering’ that will be nightmarish once the liquid telescope concept becomes truly practical. I’m sure there will be ways to surmount it, but I doubt anyone has come up with how to handle dust in the construction phase just yet.

  • ljk June 25, 2007, 14:29

    Another problem that does not seem to get much notice –
    perhaps because it was reported by a Soviet lunar rover
    in the early 1970s – is that the background glare during
    the lunar night is much higher than thought, presumably
    enough to reduce observation levels.

    Would shielding a telescope in a crater be enough to
    reduce or stop this glare? Or is it just better to have a
    telescope in free space, or perhaps on a small planetoid
    at the L2 point?

  • ljk June 25, 2007, 15:02

    NASA Science News for June 25, 2007
    NASA’s next Moon rocket is still on the drawing board, but already scientists are dreaming up big new things to do with it–such as launching giant telescopes into space.



    Find out about the Science@NASA Podcast feed at http://science.nasa.gov/podcast.htm.

  • Darnell Clayton June 25, 2007, 22:39

    I think a “free space” telescope is better for one reason: meteorites.

    It would be much easier to move a free space telescope than a huge lunar one.

    Also, how would they compensate the telescope for moonquakes? (assuming that they are semi-frequent)

  • Robin Goodfellow June 26, 2007, 5:43

    LJK, the glare you are describing is Earth-shine, a telescope situation on the far side of the Moon would not have such a problem.

    The fundamental flaw I see with all Lunar observatory proposals is why the Lunar surface is preferable to free-space. Especially for visual astronomy, I don’t think it is. One reason to put a telescope on the Moon would be the ability to “service” it relatively easily (repair it, modify the instruments, etc.), but the Lunar dust issue certainly puts a kibosh on that idea. Another reason would be if a substantial Lunar industrial base existed that could dramatically lower the cost of construction of the telescope. If you have to ship all the parts from Earth, you might as well put the thing where it can do the most science, and that isn’t somewhere where it has a limited view of the sky and limited viewing opportunities.

  • philw June 26, 2007, 9:05

    Put me in the L2 is better camp. I don’t regard the dust problem as readily (inexpensively) solvable for mirrors and such. A lunar liquid mirror scope points only in one direction, a huge limitation. What’s wrong with an L2 easily reachable site? The only disadvantage is humans working in free fall vs 1/6th g assuming manned presense, which is unlikely.

  • ljk June 26, 2007, 10:14

    One type of observatory that would greatly benefit from being
    on Luna – the far side at least – is a radio telescope. Nothing
    like 2,160 miles of rock to block electromagnetic radiation from
    that pesky blue ball nearby.




  • lee ps June 26, 2007, 17:58

    I don’t know anything about this, other than what I see is happening here on Earth. Humans, while trying to lessen the limitations of Earth based telescopes, continue to build new telescopes on the Earth. They are probably booked solid already.

    Is it true that there are only one or two perfect craters at the poles? I’m guessing to say that there are many more, and as technology and human exploration continue, the Moon will have hidden and not so hidden telescopes sprouting all over its surface, just as L2 becomes very busy. There are so, so many things to look at and we’ve only just begun.

  • ljk June 27, 2007, 16:40


    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

  • ljk June 28, 2007, 0:19

    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)


    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)


    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)


    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)


  • f June 28, 2007, 22:59

    Ijk: have you read the articles? It’s four articles and they are more than 100 pages total, it would be nice if someone else did it :-), and gave some opinion, or summary… besides the abstracts..

    It looks like the idea that TLPs are somehow connected to outgassing and radon levels are not new in itself. Have previous systematic searches just not thorough enough?

  • f June 28, 2007, 23:14

    philw: L2 is good. Maybe the main point here is you don’t have to manufacture the mirror (with extreme precision). You can integrate a certain spot on the sky for years with a perfect 30 meter mirror.

    If that’s what you want to do, it has other pros:
    -you don’t have to maneuver your telescope
    -it’s closer to Earth->greater bandwidth(probably not necessary)
    -easier to shade
    – ?

    Maybe not much…

  • ljk February 19, 2008, 11:37

    Listening to the Universe from the Far Side of the Moon

    Written by Fraser Cain

    Perhaps one of the best reasons to return to the Moon will be the boon to astronomy. Without an atmosphere, an observatory the Moon won’t have to peer through an obscuring atmosphere, but people will still be able to walk over and fix it – and even upgrade it – into the future. It’s the best of both worlds. It’s no surprise then, that engineers are working on plans for lunar observatories. When the next wave of astronauts return to the Moon, they’ll be bringing their ‘scopes.

    NASA recently selected a series of 19 proposals for lunar observatories, including one suggested by a team from MIT. This observatory would help astronomers study the “Dark Ages” of the Universe, when the first stars and galaxies, and even dark matter formed.

    During the first billion years after the Big Bang, there were no stars and galaxies, only opaque hot gas. When the first stars could finally form, their radiation helped ionize this gas and make it transparent. You could finally see in the Universe. It was also in this time that the mysterious dark matter formed from the soup of elementary particles, serving as a gravitational structure for matter to clump around.

    The MIT proposal is called the Lunar Array for Radio Cosmology, and it’s headed by Jacqueline Hewitt, a professor of physics and director of MIT’s Kavli Institute for Astrophysics and Space Science.

    It would consist of hundreds of telescope modules spread over a 2 square km area designed to pick up very-low-frequency radio emissions. Automated vehicles would crawl across the lunar surface deploying the telescopes.

    Full article here:


  • ljk June 5, 2008, 9:42

    Giant telescopes could be built from Moon dust

    NewScientist news service June 4, 2008

    Scientists at NASA’s Goddard Space
    Flight Center have created a
    concrete-like substance using a
    mixture of carbon nanotubes, epoxy
    and a crushed rock material, and
    built a 3-meter dish. Then they
    added more liquid epoxy to its
    surface and spun it, coating it with
    aluminium in a vacuum. They believe
    the process could be scaled up to
    produce 20-…


  • Marcos Passarello September 28, 2008, 11:56

    I see the diagrams of how to obtain He3 from the moon studying the papers of
    University of Wisconsin.The design of mining machine to do this process
    that go to the moon, extract He3,
    come back to earth and in the middle of the way process the he3.
    The methodology” BIA”, a matrix of all problems that the machine
    could have in the way to the moon and in the way to earth.
    The Impact found simple problems that could have the machine in the way
    To the moon, and criticals problems, always is high. The times, for develop
    the mining machine. The last matter will be work in Bio-fuels-Diesel,
    it could be good for the future analyses of how to process He3 fuels.
    I work and develop since years a methodology of Risk Space Management
    using standards 4360 AUS-NZ ,NIST -800-30 and in the end i am working
    with ISO 31000, and 31010.

  • ljk June 22, 2009, 11:47

    Sunday, June 21, 2009

    Lunar mirror to be retired

    “Among the project’s unlikely achievements has been the discovery that the moon is moving away from Earth at a rate of two-and-a-half inches a year.” A significant disclosure. In time the moon will lose its effect on the Earth and will alter Earth’s physics.

    “After 40 years’ reflection, laser moon mirror project is axed”

    US research that began with the first Apollo landing – and helped to prove that the moon is moving away from Earth – is to be axed.

    by Robin McKie

    June 21st, 2009

    The Observer

    An experiment, begun when Apollo 11 astronauts Neil Armstrong and Buzz Aldrin left a mirror on the lunar surface 40 years ago to allow Earth-based astronomers to fire lasers at it, has been ended by American science chiefs.

    The National Science Foundation (NSF) last week wrote to scientists working at the McDonald Laser ranging station at Fort Davis in Texas to tell them the annual $125,000 funding for their research project was going be terminated following a review of its scientific merits.

    The decision means that four decades of continuous lunar laser research at the McDonald Observatory, run by the University of Texas at Austin, will be halted by the end of this year. Among the project’s unlikely achievements has been the discovery that the moon is moving away from Earth at a rate of two-and-a-half inches a year.

    The mirror’s existence, and the fact that astronomers can bounce lasers off it and detect the returning beam, has also provided Nasa and other scientists with compelling evidence to refute the claims of moon-landing deniers who claim the Apollo lunar mission were hoaxes filmed in an Earth-based studio.

    Full article here: