Tuesday, March 12, 2019

Lunar water; Who dunit ??

As the world awakes to one more paper appearing at GRL [12th March, 2019] on lunar water finding by a UV instrument (LAMP) on NASA's LRO today; my memories takes me back to 14th November, 2008. The LAMP team has announced that by carefully analyzing the data they could find water molecule moving around during the day time on the moon. That day, at  ISRO's Bylalu station, our senior most team member, Prof. R.Sridharan was literally jumping around as he noticed peak number-18 (water) in our just arrived mass spectra relayed by CHACE instrument, my baby, as it took a suicidal journey on the Moon Impact Probe of Chandrayaan-I.

Credit: ESA

If I can make the story very short... it goes as follows...
A billion hearts were beating to the success of Chandrayaan-I reaching moon on 8th November, 2008. Then came the 14th November episode of Moon Impact Probe (MIP) being separated from the mother space craft and had an impact on southern pole of the moon; covering around 2,800 km with a descend journey lasting around 22-minutes. The story of CHACE (CHandra's Altitudinal Composition Explorer), the ONLY science experiment on MIP; it is best narrated in my blog here. 

CHACE has been built to sample that tiniest of tiny particle densities around 10^3 and above in the lunar ambiance. However; as the humanity had learned its lessons when Bob Hodges and his team members had built their LACE mass spectrometers and left by Apollo team members on the moon; all of those instruments were getting saturated as the sun started rising on the lunar horizon; it was later learned that the poor dynamic range as the cause. Thanks to the present day technology; the CHACE could withstand 10-orders of dynamic range; while the older versions of mass spectrometers could at best 4-5 orders. It is for this reason that CHACE came out as a WINNER. But our joy was very short lived. As we sent our manuscript both to Science and later to Nature; none of the experts were ready to believe on what CHACE had relayed by giving its own life; they called it contamination.

CHACE, a quadrupole mass spectrometer, riding on the front end of Moon Impact Probe (MIP) was over sampling the lunar ambiance as the MIP gushing though the tenuous atmosphere at the speeds of around 1.5 km/s. No one would ever believe that CHACE was actually sampling the first time ever day time lunar ambiance. It was ridiculed as outgassing  by the spacecraft inner components. By the time we realized that the "ram correction" was needed for this over sampling (10^4 higher); the other payloads on Chandrayaan-I from NASA had got their instruments (MMM and min-SAR) geared to look for reflectance signatures of water and had their work published in the same journal Science in October, 2009.   It was the same Science journal which published MMM data withing 4-5 months of rejection of CHACE observations.

Finally after an agonizing wait of one year and 2-months our work was published in February 2010. I always carry (will..... till I breath my last) this guilt of missing the bus. Today, as I read the GRL paper; I like to draw attention of each and every soul who had ridiculed our work when we were trying to bring to their notice that....  YES.... INDEED THERE IS A WATER ON THE MOON....

Chronological developments on Lunar water
1. Chandrayaan-1 Lunar orbit injection....          8th Nov. 2008

2. Moon Impact Probe mission ...                        14th Nov. 2008
(Successful CHACE observations of H2O)

3. CHACE Manuscript to Science journal..         Dec. 2008

4. Meeting of Ch-1 scientist at ISRO-HQ....        Feb. 2009
(PIs of Indian/Foreign payloads including 
MMM, mini-SAR;
CHACE plot of lunar water shown to all)

5. MMM operational .......                                    Mar. 2009

6. MMM publication in Science .....                     Oct 2009

7. CHACE Publication .....                                   Feb. 2010

8. LAMP /LRO Publication ....                            Feb 2019

Lunar water; Who dunit ??