- 22 Nov 2020
The moon which was believed to be bone dry until around a decade ago, when a series of astronomical findings suggested that there are traces of water on its surface, has lately been the cynosure of many eyes. NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) has confirmed, for the first time, water on the sunlit surface of the Moon.
Image Credits: NASA/Daniel Rutter
Scientists using NASA’s telescope on an airplane, the Stratospheric Observatory for Infrared Astronomy, discovered water on a sunlit surface of the Moon for the first time. The water molecules have been detected in the Clavius Crater,one of the largest craters visible from Earth, located in the Moon’s southern hemisphere. NASA claims that this is the first time traces of water have been discovered in lunar regions under the direct glare of the sun. As a comparison, the Sahara desert has 100 times the amount of water than what SOFIA detected in the lunar soil. Despite the small amounts, the discovery raises new questions about how water is created and how it persists on the harsh, airless lunar surface.
Why is the discovery of water on the moon important?
Apart from being an essential means for supporting life, water happens to be a precious resource in deep space. For astronauts landing on the moon, water is necessary not only to sustain life but it can also provide for generating rocket fuel.
“Water is a valuable resource, for both scientific purposes and for use by our explorers,” said Jacob Bleacher, chief exploration scientist for NASA’s Human Exploration and Operations Mission Directorate. “If we can use the resources at the Moon, then we can carry less water and more equipment to help enable new scientific discoveries.”
What is so giddy in this discovery?
Water ice in lunar soil; Image Credits:sserv.nasa.gov
Our nearest celestial neighbor is dotted with huge craters with rims sufficiently high so that sunlight never reaches inside. Previously, it has been conjectured that water can be trapped and stored in these locations, also called 'cold-traps'. As soon as the lunar surface gets hit by a water-rich asteroid or meteorite, the water necessarily ascends and if it falls back in those cold-traps, it gets stored there permanently and is never coming out. Another possibility is there could be a two-step process whereby the Sun’s solar wind delivers hydrogen to the lunar surface and causes a chemical reaction with oxygen-bearing minerals in the soil to create hydroxyl. Meanwhile, radiation from the bombardment of micrometeorites could be transforming that hydroxyl into water, needless to say everything was supposed to happen in those cold-traps.
However, if the water isn't fortunate enough and incidentally lands close to the equator and not in those cold-traps, it will take only seconds for it to evaporate, leaving no traces at all and that is exactly what makes this discovery even more amusing.
Crater Clavius:a lunar mystery; Image Credits:BBC Sky
“Without a thick atmosphere, water on the sunlit lunar surface should just be lost to space,” said Honniball, who is now a postdoctoral fellow at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Yet somehow we’re seeing it. Something is generating the water, and something must be trapping it there.”
As astrophysicist Neil deGrasse Tyson hilariously and rightly pointed out,'there happens to be no such thing as the dark side of the moon unlike the Pink Floyd album,"The Dark Side of the moon".' The side of the Moon we do not see from Earth gets just as much sunlight on it as the side we do see. It is all about those regions exposed to the direct rays of the Sun.
Scientists from NASA have been using the available information with their venerable knowledge and profundity to understand how water is exactly stored in the sunlit lunar surface. Several forces and methods could be at play in the delivery and storage of this water. Tiny bead-like structures form in the soil due to the extreme heat created by micrometeorite impacts. Water can get stored in those small fissures. Water could also be hidden between grains of lunar soil and thus sheltered from the sunlight – potentially making it a bit more accessible than water trapped in bead-like structures. As enticing as the discovery already is, it has raised a series of intriguing questions followed by an ocean of fascinating inferences.
Space is unexpected and so is life:
The mission was originally designed to look at distant, dim objects such as black holes, star clusters, and galaxies. The telescope operators typically use a guide camera to track stars, keeping the telescope locked steadily on its observing target. But the Moon, being our closest neighbor, is so close and bright that it fills the guide camera’s entire field of view. To determine if the telescopes could track the moon in absence of any other star clearly visible, in August 2018, the operators decided to try a test observation.
“It was, in fact, the first time SOFIA has looked at the Moon, and we weren’t even completely sure if we would get reliable data, but questions about the Moon’s water compelled us to try,” said Naseem Rangwala, SOFIA’s project scientist at NASA's Ames Research Center in California's Silicon Valley. “It’s incredible that this discovery came out of what was essentially a test,almost like a cold day in July and now that we know we can do this, we’re planning more flights to do more observations.”
Years of research fund to success
Image Credits: isro.gov
NASA has very clearly stated that SOPHIA'S success is definitely not a flash in the pan. Rather, it is built on years of previous research by various organizations examining the presence of water on the Moon. Orbital and impactor missions over the past 20 years, such as NASA’s Lunar Crater Observation and Sensing Satellite, confirmed ice in permanently shadowed craters around the Moon’s poles. On 18 August 1976, the Soviet Luna 24 probe landed at Mare Crisium, took samples from the depths of 118, 143, and 184 cm of the lunar regolith, and then took them to Earth. In February 1978, it was published that laboratory analysis of these samples showed they contained 0.1% water by mass. Several spacecraft – including the Cassini mission and Deep Impact comet mission, as well as the Indian Space Research Organization’s Chandrayaan-1 mission – and NASA’s ground-based Infrared Telescope Facility, looked broadly across the lunar surface and found evidence of hydration in sunnier regions. On 14 November 2008, India made the Moon Impact Probe onboard Chandrayaan-1 orbiter crash into Shackleton crater and confirmed the presence of water ice. However, this time it's more about where and exactly in which form that further adds to the gravity of the discovery.
Water is a precious resource in deep space and a key ingredient of life as we know it. Whether the water SOFIA found is easily accessible for use as a resource remains to be determined. Under NASA’s Artemis program, the agency is eager to learn all it can about the presence of water on the Moon in advance of sending the first woman and next man to the lunar surface in 2024 and establishing a sustainable human presence there by the end of the decade. In short, we are yet a few steps behind in making lavish travel plans to head there and have a swim of a lifetime.