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?