What has ISRO's Chandrayaan-2 found on the Moon?

 The observations of the Chandrayaan-2 orbiter payloads have yielded discovery-class findings, according to the Indian Space Research Organisation (ISRO). ISRO has released the information gathered, from confirmation of the presence of the water molecule to data about solar flares.


A glimpse of Chandrayaan-2 Orbiter in a clean room. It carries 8 scientific payloads for mapping the lunar surface and to study the moon's atmosphere. Image : ISRO

What has Chandrayaan-2 sent?

Although the soft landing on the Moon failed, the Orbiter has been doing its job. Earlier this week, ISRO opened up its scientific discussions on Lunar Science to "the people of the country, to engage the Indian academia, institutes, students, and people from all disciplines and walks of life", in the form of a two-day 'Lunar Science Workshop & Release of Chandrayaan-2 Data'. The workshop commemorated the completion of two years of the Chandrayaan-2 orbiter in lunar orbit.

The Orbiter part of the mission has been functioning normally, and in the two years since that setback, the various instruments on board have gathered a wealth of new information that has added to our knowledge about the Moon and its environment. 

The Orbiter is carrying eight instruments. They are: Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS), Solar X-ray Monitor (XSM), CHandra's Atmospheric Compositional Explorer 2 (CHACE 2), Dual Frequency Synthetic Aperture Radar (DFSAR), Imaging Infra-Red Spectrometer (IIRS), Terrain Mapping Camera (TMC 2), Orbiter High Resolution Camera (OHRC), and Dual Frequency Radio Science (DFRS) experiment.

Through different methods, these instruments are meant to carry out a few broad tasks — study in more detail the elemental composition of the lunar surface and environment, assess the presence of different minerals, and do a more detailed mapping of the lunar terrain.

What are some of the significant results so far?

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Image : ISRO

Water molecule : The presence of water on the Moon had already been confirmed by Chandrayaan-1, India’s first mission to the Moon that flew in 2008. But the instrument used on Chandrayaan-1 was not sensitive enough to detect whether the signals of water presence came from the hydroxyl radical (OH) or the water molecule (H2O, which too has OH ). Using far more sensitive instruments, the Imaging Infra-Red Spectrometer (IIRS) on board Chandrayaan-2 has been able to distinguish between hydroxyl and water molecules, and found unique signatures of both. This is the most precise information about the presence of H2O molecules on the Moon till date.

Chandrayaan-2 also has now found signatures of water at all latitudes, although its abundance varies from place to place. Previously, water was known to be present mainly in the polar regions of the Moon. Besides, the Dual Frequency Synthetic Aperture Radar, a microwave imaging instrument, has reported unambiguous detection of potential water ice at the poles as it has been able to distinguish properties of surface roughness from that of water ice, which is a first.

Studying the sun : One of the payloads, called Solar X-ray Monitor (XSM), besides studying the Moon through the radiation coming in from the Sun, has collected information about solar flares. XSM has observed a large number of microflares outside the active region for the first time, and according to ISRO, this “has great implications on the understanding of the mechanism behind heating of the solar corona”, which has been an open problem for many decades.

Minor elements : The Large Area Soft X-Ray Spectrometer (CLASS) measures the Moon’s X-ray spectrum to examine the presence of major elements such as magnesium, aluminium, silicon, calcium, titanium, iron, etc. CLASS has mapped nearly 95% of the lunar surface in X-rays for the first time. This instrument has detected the minor elements chromium and manganese for the first time through remote sensing. Sodium, also a minor element on the Moon surface, was detected without any ambiguity for the first time. Scientists at ISRO believe that based on the CLASS findings with respect to sodium, “a direct link of exospheric sodium to the surface can be established (with global data)”, a correlation that remains elusive till date. The finding can lay the path for understanding magmatic evolution on the Moon and deeper insights into the nebular conditions as well as planetary differentiation.

The observations (of Chandrayaan-2 orbiter payloads) have been yielding intriguing scientific results, which are being published in peer-reviewed journals and presented in international meetings," Mr. Sivan said. Chandrayaan-2, ISRO said, has the feat of imaging the Moon from 100 km lunar orbit with "best-ever" achieved resolution of 25 cm with its OHRC.

How does all these findings help?

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Image : ISRO

While the Orbiter payloads build upon existing knowledge of the Moon in terms of its surface, sub-surface and exosphere, it also paves the path for future Moon missions. A  key outcome from Chandrayaan-2 has been the exploration of the permanently shadowed regions as well as craters and boulders underneath the regolith, the loose deposit comprising the top surface extending up to 3-4m in depth. This is expected to help scientists to zero in on future landing and drilling sites, including for human missions.

Some key future Moon missions that hope to make use of such data include the Japan Aerospace Exploration Agency (JAXA)-ISRO collaboration Lunar Polar Exploration (LUPEX) mission scheduled for launch in 2023/2024. The Chinese Lunar Exploration Programme plans to establish a prototype of the International Lunar Research Station (ILRS) at the lunar south pole and build a platform supporting large-scale scientific exploration. NASA’s Artemis missions too plans to enable human landing on the Moon beginning 2024 and target sustainable lunar exploration by 2028.