Mars Loses Atmosphere More Rapidly When Nearer to the Sun

Mars has lost enough water to space to form a global ocean up to hundreds of kilometers deep.

NASA’s Hubble Space Telescope in collaboration with the Mars Atmosphere and Volatile Evolution (MAVEN) mission has claimed that the flux of water vapor from Mars to space varies greatly with the change in seasons.

About 3. 5 billion years ago, Mars had warm and wet conditions with seas and oceans and a denser atmosphere as compared to at present. Mars as one of the planets in solar system today lacks any form of life, is cold and dry. Therefore, where did all this water go?

“Indeed there could only be two outlets for the water, “Professor John Clarke of Boston University also explained. “It can freeze and may stick to the ground or the water can be decomposed to form atoms, which can fly out of the top of the atmosphere into space. ”

Hence, much of Mars water is still there in the Red Planet. It is believed that huge reserves are located at depths between 11 and 18 km from the Earth’s surface and range in composition from volcanic rock to shale. 5 and 20 kilometers that is 7. 1 and 12. 4 miles. The amount of water which is locked up within Mars is sufficient to make a GEL, or the depth of the ocean on the scale of a planet, ranging from 1 to 2 km (0. P. 62 to 1.

There are also lesser quantities in the near surface, which is called cryosol and in Mars’ polar regions. This ice is capable of subliming when the Martian summer commences, and turn directly into vapor form. Major part of this vapor moves between the Polar Regions, condensing where winter is in the northern or southern hemisphere. But some of it rises to the stratosphere where solar ultraviolet light can photodecompose molecules of water by ripping them apart into their constituent atoms. The oxygen either combines with the materials on the surface and deposit rust-red colour to mars or reacts with carbon to form carbon dioxide. On the other hand, the hydrogen atoms (or their heavier isotope deuterium) can ‘disappear’ to outer space if it acquires the escape velocity by the help of the solar wind.

For this purpose, MAVEN which has been orbiting Mars since 2014 is designed to measure this hydrogen escape.

In light of the fact that deuterium a heavy isotope of hydrogen does not escape the Martian atmosphere as easily as its lighter counterpart the measure of deuterium to hydrogen ratio (D/H) is vital to Mars. Mars continually discharge hydrogen more openly, hence the ratio of deuterium to hydrogen in the respective reservoirs rises. Since water is thought to reside on these planets from the similar source, the D/ H ratio on Mars at the initial of its evolution 3 to 4 billion years ago should be similar to the present ratio of the Earth. Nevertheless, present-day Martian D/H ratio ranges between 8 and 10-times higher than that of present-day Earth. If the primeval D/H ratio is some value and this value is divided by today’s D/H ratio and a weighted average of the ratio of hydrogen loss to deuterium loss is also taken into consideration; then it is possible to deduce as to how much water Mars has lost.

As was determined from the earlier MAVEN measurements, Mars has lost enough water into space that it would fill and create a GEL from tens to hundreds depending on the nature of the deposits. This combined with recently discovered deposits of large quantities of water ice beneath the Martian surface means that the red planet was once awash with water.

But MAVEN along with a little help from the Hubble Space Telescope has raised some questions and discovered a little bit of complexity in the Martian water loss saga. The instruments have indicated that the hydrogen loss rate varies with time and is high during perihelion which is a period Mars is closest to the sun. This corresponds to the rise of a great deal of water vapor mass flux to the middle-atmosphere due to seasonal heating. During perihelion, the southern part of Mars faces the sun; the planet has its annual dust storms. The airborne dust enhances heating of atmosphere and intensification of the absolute water vapor in the air.

At perihelion, MAVEN got the deuterium and hydrogen concentrations in the upper atmosphere that are quintuplicate and duplicate those at aphelion, which is the farthest point of Mars in the ellipse around the sun. At aphelion the rate of deuterium loss is so low that MAVEN cannot even measure it, and so Hubble becomes the main source of data. The measurements also showed that escape rates of deuterium and hydrogen are 10 to 100 times higher at perihelion stage than in the aphelion phase. Indeed being the case, whether from deuterium or hydrogen both are evidently escaping at a faster rate at perihelion and hence the only constraint remaining is the quantity of water vapour in the atmospheric air.

”Some years ago scientists believed that the Martian has a year cycle way much more active than what they thought we was 10 or 15 years ago,” said Clarke. ‘The whole environment is quite volatile, fluctuating with short-term cycles having a few hours in a Martian year for few tens of percent of the sun’s effective brightness on Mars. ’

This poses a problem when it comes to explaining deuterium loss which looks set and larger than normal thermal escape where a deuterium atom acquires energy enough to send it into space. It was found that Viking observed 1/4 D/H ratio on Mars, while to fit the observations an extra energy source is required to increase the rate of deuterium removal. It may be from the protons in the solar wind, that regularly reach the earth’s atmosphere entering into collision with the deuterium atoms, or through various chemical reactions caused by the ultraviolet solar light which further provides additional energy to the deuterium.