Imagine you could build an observatory on the Moon. What would you look for?
That was essentially the brief given to the Lunar University Network for Astrophysics Research, or LUNAR consortium, when NASA asked it to speculate about the unique astrophysics that could be done on the Moon.
The far side of the Moon has a one characteristic that makes it particularly attractive to astronomers: it is shielded from the radio broadcasts that makes astronomical observations at these frequencies all but impossible on Earth. As a result, the LUNAR consortium says it should be possible to make two kinds of radio observations that are not possible from Earth.
First is to map the distribution of neutral hydrogen in the universe in the era after the creation of the cosmic microwave background radiation and before the Universe was lit by the first stars, a period called the Dark Ages. That’s the period between about 100 and 500 million years after the Big Bang.
The red-shifted radiation emitted by hydrogen at this time is now in the radio region of the spectrum but cannot be well measured on Earth because of noise. So a decent radio telescope on the Moon would provide a unique window into this aspect of the Universe’s history.
Another idea is to study the way particles are accelerated in the heliosphere by listening for the radio emissions they produce. Again that can only be done in the radio-quiet environment that the far side of the Moon provides.
Finally, the LUNAR consortium suggest measuring the distance to the Moon and the way it changes more accurately using laser ranging techniques. That might reveal any strange gravitational anomalies and test the equivalence principle. Sadly the reflectors placed on the Moon by Apollo astronauts are not good enough for these purposes, so new reflectors need to be sent aloft.
One thing the LUNAR consortium doesn’t stretch to is an a analysis of the cost of such projects, which may have a bearing on whether they ever get built.
But judging from the parlous state of NASA’s finances, there’s little chance of these ideas getting off the ground in the forseeable future, however cheap they be.
Ref: http://arxiv.org/abs/0909.1509: Science from the Moon: The NASA/NLSI Lunar University Network for Astrophysics Research (LUNAR)