News Nation Bureau
Fri, 09 Dec 2016 17:03 UTC
The H atoms are easily able to overcome the gravitational force of a planet and manage to permanently escape into interplanetary space due to their light weight.
Researchers said that Mars has lots the majority of its water because of the ongoing escape of the H atoms.
H atoms play a crucial role in the physics that govern the upper atmosphere of the Earth. They also act as an important shield for technological assets of the societies, such as the numerous satellites in low earth orbit, against the harsh space environment.
"Hot H atoms had been theorised to exist at very high altitudes, above several thousand kilometres, but our discovery that they exist as low as 250 kilometres was truly surprising," said Lara Waldrop, Assistant Professor from University of Illinois' Coordinated Science Laboratory in the US.
"This result suggests that current atmospheric models are missing some key physics that impacts many different studies, ranging from atmospheric escape to the thermal structure of the upper atmosphere," said Waldrop.
The discovery was enabled by the development of new numerical techniques and their application to years' worth of remote sensing measurements acquired by NASA's Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite.
"Classical assumptions about upper atmospheric physics did not allow for the presence of hot H atoms at these heights," said Dr Jianqi Qin, research scientist at Coordinated Science Laboratory.
"Once we changed our approach to avoid this unphysical assumption, we were able to correctly interpret the data for the first time," Qin said.
The ultraviolet radiation emitted by the Sun is efficiently scattered by the atomic hydrogen. The amount of scattered light sensitively depends on the amount of H atoms present in the atmosphere.
The abundance and spatial distribution of this key atmospheric constituent can thus be probed using the remote observations of the scattered H emission, such as those made by NASA's TIMED satellite.
For extracting information about the upper atmosphere from such measurements, it needs to be calculated exactly how the solar photons are scattered, which falls into Qin's unique expertise.
The researchers developed a model of the radiative transfer of the scattered emission along with a new analysis technique that incorporated a transition region between the lower and upper extents of the H distribution.
The finding was published in the journal Nature Communications.