Millions of tonnes of ice on the moon
Chandrayaan-1’s momentous discoveries of water on the moon in
different forms do not seem to end. In its latest discovery, the third
so far, the spacecraft’s radar called Miniature-Synthetic Aperture Radar
(Mini-SAR) has found more than 40 craters in the moon with ice deposits.
The craters vary from two kilometres to 15 km in diameter. They are
situated in the North Pole, in the permanently shadowed regions of the
moon. The National Aeronautics and Space Administration (NASA) estimated
that there could be at least 600 million tonnes of water ice in these
craters.
The Mini-SAR is a NASA instrument that flew on board Chandrayaan-1,
which lifted off from the spaceport at Sriharikota in Andhra Pradesh on
October 22, 2008. The spacecraft carried 11 scientific instruments from
different countries, including India. This is the second NASA instrument
on board Chandrayaan-1 to discover water on the moon. Earlier, the Moon
Mineralogy Mapper (M3) detected water molecules in extremely minute
quantities on the moon’s surface soil and rocks.
Water on the moon |
An Indian instrument called Chandra’s Altitudinal Composition
Explorer (ChACE), which is a mass spectrometer and was housed in the
Moon Impact Probe (MIP), also obtained ‘very clear signatures of H{-2}0
(18 atomic mass unit, or amu) intensifying’ in the thin atmosphere of
the moon. The MIP crashed on the lunar surface on November 14, 2008
(Frontline, October 23, 2009).
Prof. Paul Spudis, Principal Investigator of the Mini-SAR experiment
at the Lunar and Planetary Institute, Houston, United States, said: “The
new discoveries by Chandrayaan-1 and other lunar missions show that the
moon is an even more interesting and attractive scientific exploration
and operational destination than people had previously thought.”
J.N. Goswami, Principal Scientist, Chandrayaan-1, called the latest
discovery ‘an interesting and new result’. He was confident that
whatever signals the scientists were getting about the presence of ice
deposits in the craters were correct. “It is quite interesting from our
perspective. We thought it would be there and it is there,” he said.
Prof. Goswami, who is also Director, Physical Research Laboratory,
Ahmedabad, pointed out that the M3 had earlier found water molecules on
the moon’s surface soil and rocks. “We are now finding it in solid form.
So this is very important. Water is an important resource if people want
to go to the moon,” he said.
The latest discovery presaged a ‘positive direction for future
explorations with respect to lunar resources and pursuit of pure
science’, said Mylswami Annadurai, Project Director, Chandrayaan-1 and
2. “Earlier, we had seen the physical phenomenon of water getting formed
in one region of the moon. We are now seeing water getting retained in
another region as ice deposits. This is called volatile transportation,”
he added.
Spudis said, “The emerging picture from the multiple measurements and
resulting data of the instruments on lunar missions indicates that water
creation, migration, deposition and retention are occurring on the
moon.” The new findings have added to the growing scientific
understanding of the multiple forms of water on the moon.
Annadurai is happy that the three important discoveries were made by
Chandrayaan-1’s instruments. “These discoveries indicate that we had a
good combination of instruments on board Chandrayaan-1. They could not
have been made by optical instruments, which need sunlight to see what
is there,” explained Annadurai.
For instance, the Mini-SAR mapped the moon’s permanently shadowed
polar craters, which are not visible from the earth. The radar uses the
polarisation properties of reflected radio waves to characterise surface
properties. Results from the mapping showed deposits having radar
characteristics similar to ice.
In the estimate of S. Satish, the spokesman for the Indian Space
Research Organisation (ISRO), the discovery had significant implications
for undertaking future missions to the moon and for interplanetary
travel.
The amount of ice estimated to be present in the craters held promise
for establishing colonies on the moon, he said. He also said, “The ice
can be used for production of oxygen for sustaining the astronauts’ stay
in the moon and to provide water to their habitat.” He predicted that
future missions would concentrate on landing rovers near the craters so
that an accurate estimate of the amount of ice available in them could
be had.
However, a scientist of the Space Physics Laboratory (SPL), Vikram
Sarabhai Space Centre, Thiruvananthapuram, cautioned that it would be
extremely difficult to set up human colonies in these permanently
shadowed regions of the moon’s North Pole. While lunar explorations with
more orbiters, landers and rovers would get a boost with these
discoveries, it was premature to talk of establishing human colonies, he
said.
T.S. Subramanian, The Hindu. |