Ladakh Expedition: An Experience of Ancient Mars
By Nidhi Goswami
Since the dawn of humanity, we have been wondering about our place in the cosmos. Are we alone in the universe? The answer to this question is obviously in the night sky, beyond the thin atmosphere of our planet. The exploration of space then seems a natural choice to move forward. However, space is vast! With current propulsion technologies, it takes days to reach the Moon, months to reach our neighbouring planets, years to cross the solar system, and would take many tens of thousands of years to reach another star! Hence, planets orbiting the Sun are currently the top priority for human exploration and settlement.
The quest to understand extraterrestrial life begins at home. Life on Earth has evolved through billions of years and has become adapted to a wide range of terrestrial environments, leading to a great diversity in life as we know it. And while Mars is one of the most researched planets in our solar system, having several rovers and landers sent to the surface of the planet, we do not yet know if life ever existed there. To help make such a determination, life in hostile and extreme environments on Earth is being researched extensively due to similar conditions to other worlds like Mars. We can understand this better via a comparative case study of the geological features of an ancient Mars analogue site on Earth outlined below.
Mars was not all rusty and rocky throughout the geological timescale; topographical evidence suggests that it might have some resemblance to present-day Ladakh, a cold desert in the northern part of India. I got a chance to visit Ladakh as a part of the Earth and Space Exploration Program (ESEP) in July 2021. It is situated at 3500 m above sea level with a lower oxygen percentage and an atmospheric pressure of 50.6 kPa – 60.8 kPa which is about half of the pressure at mean sea level (101.32 kPa). The region is also in a rain shadow zone of the Himalayas due to encasement between Karakoram Range and Zanskar Range and receives very little rainfall throughout the year. Despite the harsh weather, the natural beauty is simply breathtaking (literally!).
One can spot sand ramps at different locations of Saboo and Shey, situated near Leh [1]. Sand ramps are large dune deposits of aeolian, fluvial, and talus deposits and have developed on either side of the mountain range as a part of the regional sediment transport pathway. Sand ramps formed during the past climate hold record of the paleoclimate changes and tectonic settings of the area. Mars has a thin atmosphere with surface pressure varying from 600 Pa – 1155 Pa and a mean atmospheric pressure of 0.6% to that of Earth. Despite this, the Martian winds can reach up to a speed of 60 miles per hour resulting in the formation of dunes and dust storms. These low pressures of the Martian atmosphere lead to lower forces of sand storms when compared to that of Earth.
Tso Kar is an endorheic, high altitude, and hypersaline lake located in the southern part of Ladakh. The lake receives water from glaciers and rainfall and does not have any outflow to groundwater, river, or any other basin. As a result, there is a heavy concentration of saltwater. Contrary to the evaporation of sea or ocean water, the rate of evaporation for such hypersaline lakes at high altitudes is directly proportional to dryness in the atmosphere. Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) data from the Mars Express Orbiter have suggested the existence of 3-4 buried reservoirs of salty water near the south pole of Mars [2], although their existence is still debated in the scientific community. However, we do have a lot of evidence such as the presence of deltas in craters and the finding of minerals (clays, carbonates and sulphates) that requires water for formation towards the support of the existence of past lakes on the Martian surface. It is thought that these lakes lost their water to space or to permafrost because of the extreme climate of the red planet. This also suggests that the Martian lakes may have become hypersaline towards their end stages of life, making hypersaline lakes on Earth, such as Tso Kar at Ladakh, excellent sites similar to ancient Martian lakes.
Past satellite imagery and local evidence show that the high altitude Tso Kar lake at Ladakh is quickly drying up. During ESEP 2021, it was observed that Tso Kar has divided itself into various small ponds and the rest of the area is covered with the salt crust, which indicates an increase in the evaporation rate in the past 5-10 years. Global warming is melting glaciers at a rapid pace, thus these high-altitude hypersaline lakes may not have glacial recharge in near future — and with the increasing rate of evaporation, they may completely disappear.
Apart from hypersaline lakes and sand ramps, gullies also draw parallels between the Martian surface and Leh topography. Gullies are trenches cut into land by erosion. On Earth, they are formed by erosion due to flowing water. The gullies formation around Tso Kar lake is a consequence of glacial water activity. The formation history of Martian gullies may be varied, with ancient gullies forming due to water flow just like on Earth but data from NASA’s Mars Reconnaissance Orbiter indicate that the modern gullies are likely to be a result of the destabilisation of rocky materials by sublimation of carbon dioxide resulting in gas-lubricated debris flow [3].
The possibilities for the existence of life beyond Earth appear endless. We are just a tiny blue dot in a universe filled with galaxies and worlds. With the exploration of the survival/existence of microorganisms in our closest possible habitable neighbour, Mars, we have just begun scratching the surface of the problem. This step, however small it may appear, is very significant for our scientific endeavours. Identifying sites on Earth analogous to Mars are extremely important for testing the methods for identifying past or present life on the Red Planet. Systematic study of microorganisms in such sites will take us one step ahead to answer the question: Are we alone?
References
[1] Kumar, Anil; Srivastava, Pradeep; Meena, Narendra K. (2016). Late Pleistocene aeolian activity in the cold desert of Ladakh: A record from sand ramps. Quaternary International, S1040618216301252–. doi:10.1016/j.quaint.2016.04.006
[2] https://doi.org/10.1038/d41586-020-02751-1
[3] Stanley, S. (2016), How do gullies form on Mars?, Eos, 97, https://doi.org/10.1029/2016EO058057. Published on 26 August 2016.
Nidhi Goswami has completed her M.Sc in biotechnology from Amity University Mumbai and a Research Associate in ACOEA. She is a Research Associate for the BMSIS Young Scientist Program and is working with Dr Shiladitya DasSarma on ‘Evolution & Survival of Ancient Microbes – A Bioinformatic Approach.’