Telescopes on the Moon

 

Telescopes on the Moon

Photo by CHUTTERSNAP on Unsplash

The search is on for an Earth-like exoplanet in a solar system light-years away. Closer to home, we’ll soon be excavating the icy moons of Jupiter for life in watery realms. There’s a global drive to develop the Red Planet, Mars, where proposals include human outposts, tourism, and an intensive search for ancient life. Since the long voyage to Mars is currently too dangerous for crewed travel, robotic exploration there will likely dominate for several decades to come.

Only from the lunar surface can we mount the ultimate search for our origins. We’ll achieve this by constructing novel telescopes of unprecedented scope in dark lunar craters and on the far side of the Moon.

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As it happens, driven by a desire for extraterrestrial tourism and a new frontier for resources, we are returning to the Moon in force. The resulting lunar infrastructure will open the way to building powerful telescopes that will provide new vistas into key questions that have long obsessed humanity. Space exploration is our destiny, but we can only fulfill it, only discover the deepest mysteries of our Universe, by first returning to the Moon. Mining rare earth elements.

Lunar golf, with mile-long drives. Buggy rides on the lunar soil, or regolith. Vistas of Earth rising at lunar dawn.

Lunar mining may provide an effectively limitless supply of rare earth elements

We would establish giant lunar parks for leisure and relaxation. Mass tourism will have its day. As reserves of rare earth elements are depleted on Earth, lunar resources will step up to the task. Lunar mining may provide an effectively limitless supply of them.

Rare earth elements are central to present and future technologies. Mining companies will race to address the challenge of lunar extraction. Yet bombardment of the Moon by asteroids over billions of years has deposited trillions of tons of rare earth on the lunar surface, based on analysis of the Apollo lunar samples. Rare earth elements are mined on Earth through environmentally polluting operations.

We can limit the inevitable pollution with robotically aided extraction, and lunar launch sites will facilitate the ejection of toxic debris into space. Rare earth elements are key to present and future technologies. It will be difficult for mining companies to resist the challenges of lunar extraction. Because they are ideal for the production of rocket fuel, lunar and cislunar environments will serve as launch sites for interplanetary space probes.

The needed fuel, in the form of liquid hydrogen and oxygen, would be sourced from ice deposits in cold polar craters. Lunar fuel resources are a key component of interplanetary travel. We will make use of low lunar gravity to launch spacecraft throughout the solar system. Lunar spaceports will eventually serve as gateways to the stars.

We can build huge telescopes on the Moon to peer further back in time than we could ever do from Earth, or even in space. Giant telescopes can be constructed in dark lunar craters near the lunar poles, where the Sun never rises. Stars don’t twinkle, they shine as brilliant points of light. Such clarity is crucial if we are to search for distant planetary systems.

There are sites with unlimited solar power on the tall crater rims to power our instruments. From the Moon, we can search throughout the infrared spectrum for the elusive molecular signatures of life.

We need to search huge numbers of exoplanets for the elusive signatures of life

Such signatures may be very rare. The conditions for the origin of life are unknown. Based on what we know of the solar system, life is a rare phenomenon. We might even be alone in the Universe.

The ultimate challenge is seeking signs of intelligent life. Distant civilizations could exist. There are billions of exoplanets in our galaxy. Even if life was incredibly rare, there might well be candidates.

Such exoplanets, if inhabited, would inevitably be thousands or even millions of years ahead of us in evolution. Since the number of likely targets with signs of life is small, we need to search huge numbers of exoplanets for the elusive signatures of life. To seek out signatures of life in nearby exoplanets, future space telescopes will focus on spectral features in their atmospheres. But we will need more than spectral coverage if we are to seek robust indicators of life in the Universe.

Such relatively low-mass exoplanets are hard to detect. Exoplanets need to have rocky cores and be in habitable zones around Sun-like stars for conditions required for life as we know it. After all, that’s the only known criterion for life. This means digging deep into the infrared region of the electromagnetic spectrum.

We can’t do this from Earth, where the available spectrum is highly constrained by our atmosphere. We will build telescopes hundreds of meters in an aperture in permanently dark lunar craters.

Huge lunar telescopes will explore the first galaxies and stars in unprecedented detail

With these, we could image the nearest exoplanets, such as those around Alpha Centauri, our nearest stellar neighbor some four light-years away. The deeper we can search, the more likely we are to sample varied life-friendly environments. We don’t know what to expect, and we are certain that life is fragile and that life tracers are rare. Only by detecting unprecedented numbers of Earth-like planets can we hope to optimize our chances of finding signs of extraterrestrial life.

Huge lunar telescopes will also explore the first galaxies and stars in the Universe in unprecedented detail. They are found in the centers of galaxies. Perhaps the black holes seeded the galaxies as their violent activity triggered star formation. With large lunar telescopes, we can learn about the dawn of the Universe.

The most intimate secrets of the dark ages are best probed with a very different type of telescope, a radio telescope capable of detecting the hydrogen clouds that were the raw material of galaxies. Specifically, we will need a special type of radio telescope operating at very low radio frequencies. And the far side of the Moon is a unique site for a low-frequency radio observatory. Those longer, redshifted waves with their lower frequency are too ‘dim’ for the telescopes of today.

At such low radio frequencies, the terrestrial ionosphere simply scatters low-frequency radio waves from deep space. Terrestrial radio noise created by marine radars, radio, TV broadcasting, and cell phones all get in the way. But we won’t have this problem on the far side of the Moon, the most radio-quiet spot in the inner solar system, and the perfect place for low-frequency radio astronomy. We must go to the lowest radio frequencies.

Remember, the Universe is expanding and the energy of photons decreases with time. So detecting hydrogen at low frequency takes us back in time. The expansion of space lowers the frequency of these radio waves to the limits of what is observable. By searching for hydrogen clouds at a frequency of, say, 30 MHz, we peer back to a time long before there were any galaxies.

Sure, we have uncovered the seeds of creation, the fluctuations that seeded galaxies.