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Curiosity obtains traces of salt in the last lakes of Gale Crater

Curiosity obtains traces of salt in the last lakes of Gale Crater

The lakes on Earth turn salty on drying out and the same incident happened when the Curiosity Mars climbed to identify the younger rocks. It found some of the salts which were left behind gathering insights on life could have prospered, rather than the mere survival on Mars. Gale crater was selected in part as it provides the possibility to investigate sedimentary rocks of different ages layered on top of each other. Curiosity has found periodic clay-bearing deposits containing 30-50 percent calcium sulfate by weight as reported in a Nature Geoscience paper.

All the rocks are 3.3-3.7 billion years old dating to the Hesperian period. Likewise, rich deposits have not been found in the older rocks of the crater. According to Dr. William Rapin of the California Institute of Technology and co-authors, the salts are present due to the percolation in the rocks by the waters of the bygone lakes which were very salty. Older rocks were much less salty although they were also exposed to the waters. Curiosity might detect more recent examples even though the younger ones were never touched by water.

Like a desert lake on Earth, the waters of the Gale crater evaporated, leaving a saltier residue, but it was an intermittent process on Mars that lasted 400 million years. The rocks have been subjected to forces of weathering over this vast time period even without water, and the calcium sulfate-enhanced portions are more resistant to erosion, producing mini versions of the formations in places such as Monument Valley, where harder rocks extend above the terrain.

Curiosity found a 10-meter (33-feet) slope containing 26-36 percent magnesium sulfate, in the 150 meters (500 feet) of calcium sulfate-enriched layers. Researchers believe that before the deposition of more soluble salts, it precipitated out first.

The paper mentions that their outcomes do not compromise the life search in the Gale crater. Terrestrial magnesium sulfate-rich and hypersaline lakes are known to sustain halotolerant biota while the preservation of biosignatures may be supported by crystallization of sulfate salts.

The occasional bursts of salty water are observed even today hence it is not unique to Gale crater in having such salts. As the planet dried, sulfate deposits have been identified by Martian orbiters across several places on Mars and it is the first instance where a rover has been operated its instruments over these samples. The periodic bursts of sulfate salts found by Curiosity showed Gale crater had many rounds of drying with several wet periods rather than one single great drought.

Journal Reference: Nature Geoscience

Curiosity Cradled by Gale Crater

Curiosity has sent the images of the ideal place to find evidence of life on Mars

Although Mars looks like a dry and dusty planet, science says that it used to be warm and wet along with an atmosphere. It was in this condition for billions of years, suitable for the development of life. However, we are not sure if life existed there or not. 

Efforts to understand the ancient habitability of Mars has increased in recent years. MSL Curiosity is looking to find evidence of life which existed billions of years before around the Gale Crater, which is a dried-up lake bed and a prime spot to find evidence. 

Christopher House, Geoscience Professor at Penn State University who is also a participating scientist with the Mars Science Laboratory of NASA said that Gale Crater appeared to have been a lake environment, as the mission found finely layered mudstones in the crater. It is estimated that water would have persisted for more than a million years. Gale Crater is a complex place. Besides being a lake bed, there are minerals which provide clues to habitability in Mars. However, it was finally filled with sediment, which turned to stone and then eroded. This same process also led to the creation of Mt. Sharp in the middle of Gale Crater. However, the entire system lasted more than a billion years. Sulfate has filled many fractures, indicating that water went through the rocks, even after no lakes were being formed in the planet.

House works with Sample Analysis at Mars (SAM) and stratigraphy, sedimentology teams of Mars Science Laboratory. SAM uses instrument to heat the rock samples and mass spectrometer for measuring the molecules released by heated samples which helps to identify the types of gases released. 

Researchers are interested in the sulfur gases from sulfate and sulfide minerals as the presence of decreased sulfur minerals such as pyrite would mean that the environment might have supported life previously. This is partially due to the fact that formation of pyrite needs organic matter in the sediment. The sedimentology and stratigraphy team studies the rock layers on Mars for understanding the environment they were formed. House directs daily teleconference with the researchers few times every month for planning the operations of Curiosity on Mars for the next day.

He said that it is fun to be involved in its everyday operations for taking decisions such as where to take measurements, where to drive or which measurement to be prioritised over another one in a limited time. Each day’s time is limited by the power which the rover contains and how much it requires. He feels that it has been an important learning experience in how missions are operated and collaborate with researchers all over the world. The daily operations of Curiosity is very fast and detailed. This is a golden age of planetary science. Every new driving operation brings different fields of view with different rocks and new questions to ask. 

It is similar to a new world every time it moves, but bringing into discussion the same questions about the events which occurred months before. However, it is necessary to deal with the new landscape and perform the operations for that day. Although we know a whole lot about Mars, it is still a dynamic and fascinating place. Similar missions have shown that it was a habitable environment in the past. Missions have also shown that there occurs methane releases in Mars and volcanic eruptions not so long ago. There is a lot of interest in Mars as it is quite similar to Earth than other planets in the solar system. Venus has fully different conditions, Jupiter is a planet filled with radioactive gases and the remaining planets are far away from Sun. 

In 2014, Curiosity detected methane spikes associated with organic processes along with organic carbon compounds. The rover also found evidences of ancient stream bed on Mars in 2013 proving the presence of water in the past on Red Planet. 

Initially, the mission length of MSL Curiosity was targeted at 687 days since its landing on August 2012. However it has been going on even after 2500 days. It will keep going on until its radioisotope thermoelectric generator loses its power. 

mars curiosity drill site

Large Methane Spike on Mars detected by NASA’s Curiosity

Curiosity made the strongest detection of methane on Mars last week. The laser spectrometer instrument detected a spike of 21 parts per billion by volume (ppbv) in the Gale Crater. Mars has a presence of 10ppbv methane on an average and scientists are trying to find the reason behind high concentration than usual. We know that methane can be produced by micro-organisms also and that is why we are trying to find out the source of this spike as it may imply the presence of micro-organisms.

Paul Mahaffy, a scientist at NASA’s Goddard Spaceflight Center said that using the current measurements they can’t say if the source of methane is biology or geology or ancient or modern. Curiosity and other instruments have detected few methane elements over past years but levels rise and fall and methane seem to appear and again disappear like an alien. On Earth, we have methane’s amount as nearly 1800 ppbv in the atmosphere as measured in the year 2011 and out of the amount of methane’s ppbv, about 90 to 95 percent is caused due to the living or dead creatures. 

When the researchers looked in the solar system they found that there were plenty of other ways for the generation of methane other than biological reasons. They found out that methane can also be generated using the geological processes and there can be the generation of methane abiotically that is without the presence of life. On planets such as Jupiter, Saturn, Uranus, and Neptune, plenty of methane have emerged through chemical reactions.

Though methane’s generation is not rare in the solar system we know that Earth is the only planet which has biological processes. Pluto has methane ice whereas Titan which is Saturn’s moon has lakes of liquid methane. So the scientists can’t easily conclude that the amount of methane produced in Mars is due to the presence of living creatures or not.

The European Space Agency’s ExoMars Trace Gas Orbiter has the ability to detect almost 50 parts of methane per trillion by volume in the Martian Atmosphere and has been collecting data but is still empty-handed only.

The observations undergoing will help to figure out the detection and NASA will get more data if the gas was transient or local to Gale Crater and they have also kept contact with Trace Gas Orbiter team to see if the observation were same which would help in locating the source of gas and calculate the time it lasts in atmosphere.