The Indian space research organization ISRO
add another achievement to his name by discovering
a Suprathermal proton from different source.
A new group of suprathermal protons are discovered
near the Moon Surface by the Atom Reflecting
Analyzer experiment on first Indian lunar
mission Chandrayaan-1.
These protons are found to exist on the sun
side as well as the night side of the Moon.
Sun emits not only radiation but also a stream
of ionized particles known as solar wind.
Sun is composed dominantly of hydrogen (H)
and its ionized form is H plus, which is basically
a proton.
Solar wind is an extension of the solar corona,
which is the outermost layer of the Sun.
Solar wind flows through the solar system
and interacts with the various ions in it.
Our Earth possesses a substantial magnetic
field of its own, which effectively blocks
the solar wind and shields the planet.
On the other hand, Moon does not possess a
global magnetic field.
This results in the continuous bombardment
of solar wind on the lunar surface.
The Moon possesses a surface bound exosphere
having neutral atoms or molecules around it
including hydrogen atoms.
These atoms become ionized by the ultra-violet
radiation from the Sun, the process called
photo ionization and also due to collision
of hydrogen atom of moon with solar wind protons,
this process called charge exchange.
These suprathermal proton found up to height
of 100 to 200 km from moon surface.
But the new population of protons that are
discovered near the Moon by the Chandrayaan-1
are not associated with any of these known
sources or processes, neither by photo ionization
or nor by charge exchange.
The detailed analysis shows that the source
is located at higher altitude, more than 500
km above the day side lunar surface and their
density and velocity distribution reveals
that they are neither from interplanetary
nor interstellar medium and its origin is
still an enigma.
The yellow curve shows the sample trajectory
of the suprathermal protons, a possible way
of transportation from the source location
to near the moon where they are observed by
Chandrayaan 1.
This indicates that our knowledge about Moon
is still limited and calls for further exploration.
These observations are also important to understand
the environment of any non-magnetized body
without atmosphere in our solar system as
well as Exo-planetary systems.
