Thursday, December 19, 2013

Heavy Metals (??) on Moon by CHACE (Chandrayaan-I)

Have we found heavy metals on Moon ??

With an introduction to the present post, lets start with LADEE, then we will move over to the topic of identification of heavy metals (?) on the moon; the observations made by CHACE CHandra's Altitudinal Composition Explorer, a quadrupole spectrometer) during the Moon Impact Probe Mission  (MIP) of Chandrayaan-I (Ch-I). The sole purpose of this blog is to highlight a recent note published in Current Science; on the observation of two prominent amu (atomic mass unit) peaks at 80 and 94.

The CHACE observations were made during the very first phase of actions taken having got the Chandrayaan-I (Ch-I into 100 X 100 km polar orbit on 14th November, 2008. In a way, these were the very first set of experiments performed during the Ch-I project; while all the other payloads (instruments) were kept in hibernation. The Moon Impact Probe (MIP got separated from the mother space craft, Ch-I near the northern pole of the moon and had a 22-minute descend journey before having an impact near the south pole at Shackleton crater. The CHACE, a most ambitious and carefully planned scientific instrument worked exactly, may be a less justified word, and collected around 300-mass spectra covering 1-100 amu (atomic mass unit). The peak at amu-18 (water), standing tall like the Statue of Liberty in front of NY city was mark of jubilation to the CHACE team on 14th Nov.-2008. The present post is to bring in some light on the fag end of 60-100 amu CHACE observations in view of LADEE being sent to the Moon by NASA.

As NASA calls it Lunar Atmosphere and Dust Environment Explorer, LADEE, pronounced like "laddie"  (taken from NASA site). LADEE was launched on 6th September, 2013; a robotic mission to study the lunar atmosphere; and/or environmental influence on the lunar dust. Strange, but true; the dream of a group of scientists (the author was one among them) at ISRO was also  the same while the Moon Impact Probe mission was getting conceptualized (2003); to sample the lunar "environment" during the descend mission of MIP in Ch-I. The three instruments of LADEE are: 1. UV/Visible Light Spectrometer, 2. Neutral Mass Spectrometer and 3. Lunar Dust Experiment, the LADEE hopes to study the density, composition of lunar environment. A 100-day science mission is anticipated in an orbit ranging between 20-60 kms. 

As mentioned in the introduction;  CHACE had acquired 1-100 amu range spectra sampling the lunar ambiance during the 22-minutes of MIP descend till it had an impact near the lunar southern pole. We succeeded in our first publication on discovery of water with a laborious period of convincing the international scientific community for ONE year and 4-months (March-2010); the second paper describing a large chunk of data appeared in August-2010. 

We have just got a paper published in Indian journal Current Science on the heavy species observed by CHACE in 60-100 amu. The CHACE spectra also had shown some striking features on appearance of high mass peaks at 77, 78, 79; however the species at amu=80 and 94 were very pronounced. A sample spectrum at an altitude of 100 km in the 60-100 amu range is shown here.

CHACE Spectra; 60-100 amu
(Credit: Current Science, 1470, 105, 2013)

Unlike earth, any particle in the lunar ambiance is known to have the surface boundary exosphere (SBE); meaning that the particles may not be having any collisions and each species is characterized by its own SBE. So, in a way, any identification of sampled species during the descent journey of MIP reflects the elemental presence of those species on the ground.

What are amu nos. 80, 94 ??
Since these are FIRST of its kind measurements; it is very interesting to get an answer for this question. THESE COULD BE ELEMENTS OR COMPLEX MOLECULES. Elemental because the path traversed by MIP was over the KREEP region and hence could be of rare earth category. However, we all look forward to LADEE picking up these and many more species upto 150 amu.  

I like to draw your attention to my blog on the Indian instrument, CHACE, which has observed for the FIRST TIME EVER the lunar daytime composition

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