‘Rocks from Sithampoondi, Kunnamalai are similar in properties to moon soil’

At the lunar terrain facility of the Indian Space Research Organisation in Bangalore is a big spread of the “lunar” simulant soil. As commands erupt into life, a 17-kg rover, akin to the rover of Chandrayaan-2, revs up. It turns right, then left, lurches forward and backs up. Applause from a group of ISRO engineers fills the air.

About 260 km away, villagers of Sithampoondi and Kunnamalai, 65 km from Salem on the Salem–Tiruchengode highway, cannot wait for the rover from Chandrayaan-2 to land on the moon in 2017. For, the “lunar” soil on which the rover goes through its paces in Bangalore is from their villages. Anorthosite rock from Sithampoondi and Kunnamalai, which closely resembles the lunar soil in the latter’s chemical and mechanical properties, was pulverised and brought to the lunar terrain facility in the ISRO Satellite Integration and Testing Establishment (ISITE) in Bangalore to test the rover’s movements.

M. Annadurai, Programme Director, Indian Remote-sensing Satellites and Small Satellites Systems, ISRO, said: “We identified Sithampoondi, from where we excavated 60 tonnes of rocks which are geologically similar to the lunar composition. We made a special effort to pulverise the rocks to various sizes ranging from 30 to 200 microns and mix them in various proportions to match the chemical and mechanical properties of the lunar soil to study the rover’s movements on it in a simulated environment.” Since the gravity on the moon is one-sixth of the earth’s gravity, a helium-filled balloon which will lift five-sixths of the rover’s weight is being used in the lunar terrain facility.

“We have realised a six-wheeled rover and it is being tested in the lunar terrain facility. The design work on the lander is in progress in ISRO. Everything about the Chandrayaan-2 mission is Indian. The launch vehicle, the orbiter, the lander and the rover are all from India,” Dr. Annadurai emphasised.

Geologists from Periyar University, Salem; the National Institute of Technology, Tiruchi; the, Indian Institute of Science, Bangalore, and the National Geophysical Research Institute, Hyderabad, “concurred” that the rocks from Sithampoondi and Kunnamalai were similar in properties to that of the soil on the moon, Dr. Annadurai said.

Special study on lunar soil

S. Anbazhagan, Professor and Head of the Department of Geology, Periyar University, said: “We had done spectral studies on the lunar soil and we discovered its equivalent at Sithampoondi in 2004 when I was working in the Indian Institute of Technology-Bombay. ISRO’s soil scientists coordinated with us in this project.”

The moon has two types of rocks — basaltic and anorthosite. The latter covers a vast area of the moon. “The chemistry and mineralogy of the rocks at Sithampoondi are the same as that of the lunar soil,” added Dr. Anbazhagan.

The Geo-synchronous Satellite Launch Vehicle (GSLV-Mark II) with an indigenous cryogenic engine will put Chandrayaan-2 in orbit in 2017.

A lander from the orbiter will land on the moon. From the lander, the rover will roll out on to the lunar soil. The rover will move about on the high latitude area of the moon and conduct experiments.

Weighing 20 kg, it will move about on the moon for one lunar day, that is, 14 earth days, Dr. Annadurai said. It would be loaded with commands for turning to the left and right, for going forward and backing down.

The rover will carry two instruments, laser-induced breakdown spectrometer and alpha particle-induced X-ray spectroscope, to study the chemical properties of the lunar soil.

As for D. Selvaraj and S. Suresh, two young men from Kunnamalai, they cannot wait for the GSLV lift-off with Chandrayaan-2 on board. “Sithampoondi and Kunnamalai villagers are happy that the rocks from their villages are being used to test the Chandrayaan’s rover,” they said.

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