As the third installation of the Chandrayaan lunar programme by ISRO prepares for its launch, let’s take a look at when the Chandrayaan-1 mission helped discover water on the moon’s surface:
About Chandrayaan-1
On October 22, 2008, India launched the Chandrayaan-1 spacecraft into Earth orbit using a PSLV rocket. After performing orbit-raising maneuvers, Chandrayaan-1 successfully entered orbit around the Moon on November 8 of the same year.
Over the next four days, it used its engines at specific intervals to achieve a circular orbit around 100 kilometers (62 miles) above the Moon’s surface. This allowed the spacecraft to closely study the Moon using its 11 instruments, with about half of them provided by NASA and European space agencies. Communication with the orbiter was lost on August 29, 2009, but the mission accomplished its main objectives, including the discovery of water on the Moon, according to a report by The Planetary Society.
The idea of launching Chandrayaan-1 originated from Dr. K. Kasturirangan, the former chair of ISRO. He envisioned ISRO’s involvement in India’s ambition to become a superpower, and the concept of a Moon orbiter received positive feedback. ISRO already had satellites designed for geostationary orbits, which could carry ample fuel. With some modifications, a geostationary satellite could be adapted for a lunar mission. Chandrayaan-1 became a natural progression of ISRO’s capabilities.
Discovering water on the Moon was a significant scientific goal of the Chandrayaan-1 mission. NASA contributed two instruments, the Miniature Synthetic Aperture Radar (Mini-SAR) and the Moon Mineralogical Mapper (M3), to aid in the search for water. Mini-SAR detected patterns consistent with water ice in the reflections from polar craters, while M3 analyzed how the lunar surface reflected and absorbed infrared light to confirm the presence of water. M3 also provided valuable data on the distribution of water and hydroxyl across the Moon. These findings were crucial for future lunar missions and understanding the Moon’s origin, the report explains.
A Deeper Look at the Mission
In addition to Indian instruments, the spacecraft carried scientific equipment from the United States, the United Kingdom, Germany, Sweden, and Bulgaria, as per NASA.
After launch, Chandrayaan-1 entered an initial geostationary transfer orbit. Over 13 days, the spacecraft performed five burns of its liquid engine to raise its orbit to higher apogees (the point in the orbit of the moon or a satellite at which it is furthest from the earth), reaching distances of 37,900 kilometers, 74,715 kilometers, 164,600 kilometers, 267,000 kilometers, and 380,000 kilometers.
On November 8, after a 13.5-minute burn, Chandrayaan-1 successfully entered lunar orbit. Over the following days, the spacecraft gradually reduced its orbit to achieve an operational polar orbit at around 100 kilometers above the lunar surface.
Two days later, Chandrayaan-1 released its Moon Impact Probe (MIP), weighing 29 kilograms. The probe descended, collecting data with its instruments until it crashed onto the lunar surface near the Shackleton Crater at the south pole of the Moon, as per NASA.
During the MIP’s descent, data from Chandra’s altitudinal composition explorer (CHASE) indicated the potential presence of water in the lunar atmosphere, although further verification was necessary for conclusive evidence, the report by NASA explained.
In late November 2008, Chandrayaan-1 experienced abnormally high temperatures, leading to operational limitations where only one scientific instrument could be used at a time.
In May 2009, Chandrayaan-1 was placed into a higher orbit of 200 kilometers in an attempt to manage the temperatures on board the spacecraft.
During its operation in lunar orbit, Chandrayaan-1 encountered a failure in one of its star sensors after nine months. The backup sensor also failed shortly after, resulting in the primary attitude control system becoming inoperable. Controllers then relied on a mechanical gyroscope system to maintain the spacecraft’s proper attitude.
The last contact with Chandrayaan-1 occurred on August 28, 2009, falling short of its planned two-year lifetime. However, the Indian Space Research Organisation (ISRO) stated that at least 95% of the mission objectives had been accomplished by that point. The mission likely ended due to the failure of the power supply caused by overheating.
One of the significant discoveries made by Chandrayaan-1 pertained to the presence of water on the Moon. In September 2009, scientists published results based on data collected by the American M3 instrument, which detected absorption features on the polar regions of the lunar surface associated with hydroxyl- and/or water-bearing molecules, as per the report.
This finding was further supported in August 2013 when evidence of water molecules locked within mineral grains on the lunar surface was announced. This water, known as magmatic water, originates from deep within the Moon’s interior.
Apollo astronaut samples had previously revealed the presence of magmatic water, but Chandrayaan-1’s M3 instrument was the first to detect it from lunar orbit. Prior indications of water molecules and hydroxyl were also observed by NASA’s Cassini mission during a flyby of the Moon in August 1999 and by NASA’s Deep Impact-EPOXI mission in June 2009.
What is Magmatic Water?
Magmatic water refers to water that is formed or contained within molten rock, known as magma. It originates from deep within the Earth’s mantle and is associated with volcanic processes.
When magma rises towards the Earth’s surface during volcanic activity, it can carry dissolved water in the form of hydrothermal fluids or water vapor. As the magma cools and solidifies, the water becomes trapped within the resulting igneous rocks, such as basalts or granites. This water is referred to as magmatic water.
As per a report by EarthSky, for a long time, scientists believed that rocks from the Moon were completely devoid of water and any water detected in Apollo samples was considered to be contamination from Earth. However, new laboratory techniques used in the investigation of lunar samples and data from orbital spacecraft challenged this notion.
The analysis of lunar samples revealed that the interior of the Moon is not as dry as previously thought. Additionally, orbital spacecraft detected water on the lunar surface, suggesting the presence of a thin layer formed by the interaction of solar wind with the lunar surface.
To investigate the origin of this surficial water and gain insights into deeper magmatic water within the lunar crust and mantle, scientists examined the lunar impact crater Bullialdus. The M3 instrument, carried on the Indian Space Research Organisation’s Chandrayaan-1 spacecraft in 2009, fully imaged this crater.
The researchers discovered that Bullialdus crater exhibited a significantly higher amount of hydroxyl, a molecule consisting of one oxygen atom and one hydrogen atom, compared to its surroundings. The presence of hydroxyl absorption features indicated hydroxyl bound to magmatic minerals that were excavated from depth during the impact event that formed the crater.
The identification of internal magmatic water in Bullialdus crater provides valuable information about the Moon’s volcanic processes and internal composition. It contributes to our understanding of lunar formation and how magmatic processes evolved as the Moon cooled., the report explains.
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