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Vikram helps orbiter look for water on lunar surface


BENGALURU: Hope of Indian space scientists to re-establish contact with Chandrayaan-2’s lander Vikram, lying on the lunar surface, may be fast fading with the light on the moon. But Vikram may well be a ‘martyr’ for a scientific cause. The lander, in its ‘last moment’ of impacting the lunar surface on September 7 has helped expose subsurface material to the scrutiny of a powerful payload onboard Chandrayaan-2 orbiter, which could reveal valuable data about presence of water or minerals under the surface near the lunar south pole.

A senior scientist from Indian Space Research Organisation (ISRO) told The New Indian Express that although Vikram could not play its intended role of achieving a soft-landing and enabling the robotic rover Pragyan to roll out, to conduct lunar surface exploration, its hard impact on the lunar surface has left a little crater, big enough for Chandrayaan-2’s powerful Imaging Infra Red Spectrometer (IIRS) to scrutinise the ‘dug out’ subsurface material. Water molecules are known to be below the layer of fine dust on the lunar surface, which are now exposed to the orbiter due to the lander’s impact.

“It (IIRS) is very likely to detect water molecules or minerals in higher densities than found by NASA’s (US’ National Aeronautics & Space Administration) imaging spectrometer, Moon Mineralogy Mapper (or M-cube) onboard Chandrayaan-1 spacecraft in November 2008,” the senior space scientist said.

“So, Vikram in Chandrayaan-2 mission has played the role that Moon Impact Probe (MIP) played in Chandrayaan-1 mission to provide the then breakthrough discovery of water molecules on Moon. We believe there is every chance now that IIRS on the orbiter will detect something new for us. The data is already being transmitted to the Indian Deep Space Network (IDSN) (at Bylalu near Bengaluru) and is being analysed. But it will take time to arrive at conclusions.”

On November 14, 2008, at 8.06 pm, Chandrayaan-1 had released the ISRO-made MIP which was intentionally crashed into the lunar surface at precisely 8.31 pm. This event led to the breakthrough discovery of water molecules on the moon - by MIP itself, moments before crashing, and moments later by the M-cube, which scrutinised the lunar dust plume caused by the probe slamming into the lunar surface. 

Interestingly, while NASA announced the finding on September 24, 2009, ISRO announced it a day later reporting the MIP’s findings relayed back to Chandrayaan-1 just before MIP hit the lunar surface. ISRO scientists said IIRS on board the Chandrayaan-2 orbiter is more powerful than NASA’s M-cube on Chandrayaan-1. It has a first-time capability of mineralogical and volatile mapping of the lunar surface in the spectral range of 0.8-5.0 micrometres (1 micrometre is one-millionth of a metre), and complete characterisation of water/hydroxyl features near 3.0 micrometres (also for the first time) at high spatial resolution of about 80 metres and high spectral resolution of about 20 nanometres (1 nano-metre is one-billionth of a metre).

Another ISRO scientist said Vikram, weighing 1,471 kg (245 kg on moon as its gravity is one-sixth that of earth’s), would have raised a considerable lunar dust plume on impacting the lunar surface near the south pole although the velocity with which it impacted was much less than that of the MIP, weighing 34 kg (5.6 kg on moon). 

However, this was not the role Vikram was expected to play. ISRO scientists would have preferred the much-awaited soft-landing near the moon’s south pole, a capability that would have given ISRO another feather in its cap. However, as time runs out on Vikram as the lunar night looms large from September 21-22 (the region will be in complete darkness for 14 earth days with temperatures dropping to as low as -150 degrees Celsius), ISRO scientists feel that Vikram has at least played a part in this mission, by scooping up a layer of lunar dust to expose it to the IIRS scrutiny. In doing so, Vikram might well end up a ‘martyr’, they felt.