Rishiraj Bhagawati Jul 30, 2018 15:06 PM IST
Days before Mars is scheduled to record the closest distance from Earth in 15 years, scientists have reported having spotted a sizable salt-laden lake under the ice on the southern polar plain of Mars, a body of water that raises hopes that more water — and maybe even primitive life — exists on the Red Planet.
The reservoir that was detected — about 20 kilometres in diameter, shaped like a rounded triangle and located 1.5 kilometres beneath the ice surface — represents the first and the largest stable body of liquid water ever found on Mars, said the report in the journal Science. "Water is there. We have no more doubt," co-author Enrico Flamini, the Italian space agency's Mars Express mission manager, said.
Is this new?
Previous research had already found possible signs of intermittent water flowing on the surface of Mars, so how is this discovery offering something new?
Scientists say the answer lies in the kind of water body that was observed.
"Now we are talking about a potential lake. What we talked about in 2011 and 2015 are probably transient liquid water on the surface — the key word here being "transient", in that its existence on the surface is temporary. What these guys are talking about is a stable body of lake. If this is indeed the case, then the findings are huge and could have important implications for our search for habitbale environments on Mars," Lujendra Ojha, a planetary scientist at the Johns Hopkins University in Baltimore, United States, told tech2.
"Of course we need to be cautious at this time to make sure that this indeed is a lake," Ojha, who is credited with discovering flowing liquid salt water on the surface of Mars back in 2011, quickly added.
This discovery is significant because it is the first direct evidence of liquid water on Mars, Somak Raychaudhury, director of the Inter-University Centre for Astronomy and Astrophysics (IUCAA) in Pune, said.
"Most of the early speculation, based on observations from Earth, starting from Giovanni Schiaparelli and Percival Lowell, have been proved to be unfounded. Recently, there has been some evidence through images sent from equipment in Mars that appear to show dry lake beds. This evidence is weak compared to this direct detection of a substantial body of (not flowing) water trapped deep below the surface ice," he said.
Professor Mayank Vahia from the Department of Astronomy and Astrophysics at TIFR, Mumbai, says that although there is a fair amount of water that has been observed, the reflection from the water body indicates that it is unlikely to be pure water. "At this stage, it is not even clear whether it is a lump of mud or it is largely water which is salty. But this is interesting either way," he said.
However, the kind of water that has been now observed will not be easy to investigate for signs of life or chemical nature because it is buried deep underneath the Martian surface. "Radiowave instruments that we now use will never tell you about life — you will actually need a physical sample and digging one mile on Mars will be far from easy," Vahia said.
For those wondering how the water found at Mars' south pole is still liquid, given how cold poles are, Ojha explains: "On Mars, you have a lot of exotic salts. The only way you can have liquid water at the south pole of Mars is if the water is saturated with exotic salts such as perchlorates, chlorates, and/or sulfates."
The discovery was made using a radar instrument on board the European Space Agency's Mars Express orbiter, which launched in 2003.
The tool is called the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) and was designed to find subsurface water by sending radar pulses that penetrate the surface and ice caps. MARSIS "then measures how the radio waves propagate and reflect back to the spacecraft," the study said.
A team of researchers led by Roberto Orosei of the National Institute for Astrophysics in Bologna, Italy, surveyed a region called Planum Australe, located in the southern ice cap of Mars, from May 2012 until December 2015. A total of 29 sets of radar samplings showed a "very sharp change in its associated radar signal," allowing scientists to map the outlines of the lake.
"The radar profile of this area is similar to that of lakes of liquid water found beneath the Antarctic and Greenland ice sheets on Earth, suggesting that there is a subglacial lake at this location on Mars," the report said.
Researchers said they are not sure how far down it goes, but that it may be around three feet (one metre) deep.
Does this indicate life on Mars?
Space agencies try to find traces of contemporary water because such discoveries are key to unlocking the mystery of whether life ever formed on Mars in its ancient past, and whether it might persist today.
"The discovery of this lake adds to the proof that Mars was once active, at least geologically and chemically, but the question to answer now is whether those processes were enough to produce life. This study made it clear that Mars may have been livable once. Frankly, we have absolutely no clue how life arose on Earth as well, but we have our theories," Vahia said.
Ojha, too, said he was sure that this discovery would have excited a lot of astrobiologists, "but as I said before, we need to be cautious before jumping on this. We need to exterminate any shred of doubt that this might not be a lake."
However, even after this is confirmed and if life forms are indeed observed, they are likely to be very primitive life forms such as microbes.
Moreover, the search for life on Mars has not been confined to the search for liquid water. Last month, NASA's Curiosity rover found "tough" organic molecules in three-billion-year-old sedimentary rocks near the surface, as well as seasonal variations in the levels of methane in its atmosphere.
Organic molecules include carbon and hydrogen, and also may contain oxygen, nitrogen and other elements. While usually associated with life, organic molecules also may be created by non-biological processes, and are not necessarily indicators of life, NASA pointed out. But for scientists, these findings are always encouraging.
"With these new findings, Mars is telling us to stay the course and keep searching for evidence of life," Thomas Zurbuchen, senior official at NASA, said. "I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet."
The challenges of Mars exploration
Going to Mars is not only very expensive, but also extremely difficult. Before this discovery, the biggest lessons about Mars were learnt almost exclusively from data collected by NASA's probes to the Red Planet. "The reason we get data mostly from NASA is that many countries have spectacularly failed to reach Mars. Indians were the only ones to get it right the first time itself," Vahia said.
With this discovery and other recent papers on the Martian surface, can we expect more ambitious space programmes to Mars in the coming years? Perhaps those that can eventually drill into its surface and reveal what kind of water and soil exist beneath? "I am certain this will happen," Raychaudhury said.
"Drilling won’t happen within the next generation since heavy equipment transfer will have to wait for better technology. The discovery of water might enhance the focus on Mars missions."
Ojha agrees, and adds that mission structures will have to be reconsidered by space agencies.
"The path forward with NASA seems to be a sample return mission. There is a dedicated mission to Mars that is going to probe down to 5 metres deep, but that mission is to find out how much heat is escaping from the interior of Mars."
"Maybe this is the time for India and China to take the lead in Mars exploration," Ojha said.
The Mars Orbiter Mission, better known as Mangalyaan, is India's own space probe orbiting Mars since 24 September 2014. It is India's first interplanetary mission, a mission that made ISRO the fourth space agency to reach Mars, after the Soviet space program, NASA, and the European Space Agency. But has it been helpful so far?
"Our scientific data has not been very strong from Mangalyaan. If you ask how much science has come out of it, there isn’t much. People were just happy that the instrument reached in the first attempt — they did not take enough measures to get all the data back properly," Vahia said.
He explained that Mangalyaan also has a highly elliptical orbit, so when it gets close it can study the planet properly, but when the probe gets far in its orbit, it can get 66,000 kilometres far from Mars. "In principle, the instruments on Mangalyaan had a specific detector for Methane, but I don’t know of any scientific results from the spacecraft."
"Mangalyaan has an imaging camera for the surface of Mars which has imaged many features but not specific to water. The second mission might have more instruments which are more specific to finding evidence of water," IUCAA director Raychaudhury said.
With inputs from agencies