Why moon matters for future interplanetary missions
Moon will likely be the base for future interplanetary missions. A presence there is of strategic importance.
A set of radio astronomers at NCRA are especially interested in events soon after the Big Bang, with which the universe is supposed to have been born, 13.8 billion years ago. Optical telescope can only look back to about 500 million years after the Big Bang. Radio telescopes alone can peer into the secrets beyond that. But radio telescopes like GMRT are running into a problem on the earth — interference from mobile towers and other electronic equipment.
Sometime in the near future, when the moon opens up for scientists to set up experiments, radio astronomers will be among the first set of scientists to exploit the radio-quiet zones there. A network of radio telescopes on the moon can peer deep into space without electrical interference. With proven expertise in telescope-building, India will be an automatic partner for international projects to build radio telescopes on the moon.
When the GMRT was built 20 years ago, Khodad was a quiet village. Now mobile towers have sprouted everywhere, and radio astronomers at NCRA have had to develop clever ways to weed out the noise. Now no place on the earth is free from signal interference.
The echo of electrical signals from the earth can reach even the near side of the moon, but telescopes on its far side will be completely free from interference. “The far side of the moon is completely shielded from the earth,” says Yashwant Gupta, director of NCRA. “Setting up a telescope there is like a dream.”
Radio astronomers have been watching the moon keenly for a few decades, hoping to set up their telescopes on the satellite one day. Powerful and sensitive radio telescopes, free from interference, can probe deep questions about the evolution of the universe. Optical telescopes can look back only to a point after the first stars were born. Radio waves carry information about early structures in the universe like the first stars and galaxies. They are also supposed to carry information about the first atoms in the universe, which may have formed 380,000 years after the Big Bang. But these signals are so feeble — less than a trillionth of the energy of a mobile phone signal — that astronomers need to weed out all noise. While radio astronomers want to use the moon to figure out events in the early universe, planetary scientists want to explore it to figure out how the solar system was formed, and how the earth evolved into its present state. The composition of the moon and the earth are so similar that it is sometimes hard for a geologist to figure out where a rock or soil sample has come from. But there is a crucial difference.
The moon is supposed to have been hived off from the earth when both were still hot, some 4.4 billion years ago, by the impact of a body roughly the size of Mars. It is the reason why the earth and the moon are so similar. However, the earth has evolved while the moon is frozen in time.
The earth has plate tectonics that gradually erases history from its surface. The moon died geologically a billion years ago. Or, so we thought. Recently, scientists have noticed some geological activity on the moon, but it is not of the kind that will erase history on the surface. The moon has had large volcanic eruptions like the earth, but the last major set of eruptions happened 3.2 billion years ago.
Lacking an atmosphere, the moon does not have weather, and so the surface remains largely intact. Looking at the moon is like looking at the earth a long time ago. “The Moon is the closest image of the ancient earth,” says Deepak Dhingra, assistant professor at IIT Kanpur. Dhingra, who had worked on Chandrayaan-1 while at the Physical Research Laboratory (PRL) in Ahmedabad, is a planetary scientist who studies lunar crust evolution. Our understanding of the moon has improved in recent times. The most important in the last decade was the presence of water on the moon. Scientists have detected a small layer of water all over the moon. Multiple missions, including Chandrayaan-1, have confirmed the presence of water on the poles. Recent research has also indicated that there is water inside the moon.
If there are large amounts of water on the moon, it may become easier to set up a base there. Apart from sustaining life, water can be split to generate hydrogen and oxygen, and they can serve as fuel during the long lunar night (one lunar night lasts about two earth weeks). It also removes the need to carry water from the earth when setting up bases.
The Apollo missions brought back 380 kg of samples, of which 50% was preserved for five decades. This was because NASA knew that technology to analyse the samples will improve in the future, & so didn’t want to waste them. These samples were opened and distributed this year to scientists who wanted to study them. “There will be a lot of discoveries soon,” says Dhingra.
The Indian moon missions have been driven by a combination of scientific and strategic factors. The moon will be a base for planetary exploration, and being present there will be of strategic value for any country. It is the reason why the US, Europe, Russia, China, India, Japan, South Korea and a few other countries are all planning moon missions in the future. Scientists will continue to piggyback on many of these technology-led missions. And hope for exciting discoveries over the next few decades.