Start thinking about large telescopes on the Moon and the imagination quickly runs riot. With no atmosphere to contend with, a 50-meter instrument of the sort now under discussion would be able to dwarf what telescopes can do on Earth. Exoplanet detections would be commonplace, but that’s only a beginning, for this kind of telescope could take the spectra of the planets it finds and search for biomarkers.
Ponder this: Even a twenty-meter telescope would be seventy times more sensitive than Hubble, and able to detect objects 100 times fainter than what the James Webb Space Telescope will be able to see.
Now think about putting two telescopes on the Moon. Space them widely to take advantage of interferometry, creating an instrument that can, in essence, act as a single collecting surface. Mixing such possibilities with current work on detecting exoplanetary oceans and continents, we would be able to move quickly from the indirect signature of planets found by radial velocity, microlensing and transit methods to full-scale observation of planetary surfaces, key to the search for terrestrial-style worlds.
The trick, of course, is to get the necessary equipment to the Moon, but ponder the words of Peter Chen (NASA GSFC and Catholic University):
“We could make huge telescopes on the moon relatively easily, and avoid the large expense of transporting a large mirror from Earth. Since most of the materials are already there in the form of dust, you don’t have to bring very much stuff with you, and that saves a ton of money.”
Useful stuff, that dust. But Chen’s team has more than a few tricks up its sleeve. By using carbon nanotubes instead of carbon-fiber composite materials, they can bypass the need for glass to make telescope mirrors. The idea is to mix the carbon nanotubes with epoxies and lunar dust (the team used crushed rock of the same size and composition in their work) to create materials that can be spun to create a mirror blank. Coat this with aluminum and a highly reflective telescope mirror emerges. Says team member Douglas Rabin, “Our method could be scaled-up on the moon, using the ubiquitous lunar dust, to create giant telescope mirrors up to 50 meters in diameter.”
Spin-offs are also useful, and it doesn’t hurt the funding case one bit that this composite material could also be used to build the necessary habitats for a lunar base, not to mention mirrors needed for solar-power generation. Which goes to show that lunar dust, available in considerable abundance, can quickly be turned to our advantage. Sustaining a lunar observatory of this kind would inevitably lead to other kinds of science, including radio telescopes on the far side, placed so as to be free of present and future RF interference. All in all, a fine set of implications for a modest internal project at NASA running on a shoestring budget!