Curiosity

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

Curiosity is the last and most advanced rover from NASA. It carries several instruments for scientific investigation. One of the goals is to find signs of life on the Martian surface or a few centimeters below.

Curiosity took off on November 26, 2011 atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida. It landed on August 6, 2012 in Gale Crater in the Aeolis quadrangle at 4.5895 degrees S and 137.4417 degrees E. It's landing was in the northern part of Gale Crater. Curiosity nailed its landing—“so close to the target that the offset was almost equivalent to a rounding error.” Its destination, Gale Crater, was chosen because it contained a large layered mountain. The mountain’s original name was Mt. Aeolis, but it has been changed to Mt. Sharp in honor of Robert P. Sharp (1911–2004), a field geologist and professor at Caltech. The original name Mt. Aeolis came from Greek mythology, it was a floating island where winds were held in a cave inside a mountain. With a height of 18,000 feet (3.4 miles--5.5 Km), Mt. Sharp is higher than any mountain in the continental United States. “Bradbury,” after the famous science fiction writer Ray Bradbury was picked for the name of the touchdown spot.

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  Curiosity Rover descending to surface with parachute, as photographed by HiRISE.

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  Three rovers with engineers for scale Sojourner is in the front. Spirit/Opportunity is to the left. The largest is Curiosity to the right. The setting is JPL's Mars Yard testing area.

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  First two full-resolution images of the Martian surface from the Navigation cameras The eroded rim of Gale Crater is in the distance. The foreground shows two zones of excavation probably made by blasts from the rover's descent stage thrusters.

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  View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp

Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments. Peace Vallis is a stream that ran off of the north rim of the crater.

Spacecraft

Curiosity has a mass of 1,982 pounds max (899 kilograms). It is 10 feet (3 meters) long, 9 feet (2.7 meters) wide, and 7 feet (2.2 meters) tall. Power is provided by a radioisotope thermoelectric generator that provides (about 2,700 watt hours per sol). However, it does not generate much instant power. Instead it is slowly charging its batteries all the time. When the batteries have a good charge, they can supply Curiosity with all the power it requires. It uses two rechargeable lithium-ion batteries with each having a capacity of about 42 ampere-hours.

Events for Curiosity’s landing

It employed an interesting, though complex, method of landing. Because it had so many instruments and mass it could not use the bouncing air bags that other successful rovers had used. First parachutes slowed the craft, and then four engines fired to just about stop the descent. With the vehicle basically floating above the ground, it was lowered down a “umbilical cord.” Upon safely landing, the cord was cut and the descent stage flew away at full throttle. This new scheme of landing is called the Sky Crane maneuver. Curiosity is a rover, but a very slow rover. Its top speed is 450 feet/hour—less than a quarter mile/hour. Many seem to believe that we should stick to an unmanned approach to exploration. However, remember the Apollo astronauts went 8-11 miles/hour on the far rougher terrain on the moon.

Instruments

Cameras on Curiosity

Mast Camera (Mastcam)

Mars Hand Lens Imager (MAHLI)

Mars Descent Imager (MARDI)

Spectrometers: Alpha Particle X-Ray Spectrometer (APXS)

Chemistry & Camera (ChemCam)

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin) Sample Analysis at Mars (SAM) Instrument Suite

Radiation Detectors: Radiation Assessment Detector (RAD)

Dynamic Albedo of Neutrons (DAN)

Environmental Sensors: Rover Environmental Monitoring Station (REMS)

Atmospheric Sensors

Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI)

Findings

Water

Just days into its mission, Curiosity discovered strong evidence of an ancient streambed where water once flowed knee-deep. As the mission progressed, more and more signs of water accumulated. Great amounts of past water had been suggested by most scientists based upon decades of data from both orbiting satellites and lander/rovers. Mariner 9, Viking 1, Viking 2, Mars Odyssey, Mars Global Surveyor, Mars Express, and Mars Reconnaissance Orbiter all have imaged features resembling river valleys. Many researchers believe there have been lakes on Mars. Some have developed a argument for an ocean covering a full third of the planet. The Phoenix Mars Mission actually found ice in the soil and there may have been drops of liquid water observed that formed with the heat of the descent engines. The Mars rovers Spirit and Opportunity have found evidence for a watery past. However, the vast and varied amounts of data from Curiosity have sealed the case for a wet, early Mars. It is now accepted that a large, long-lived lake existed in Gale Crater. The presence of water is a prerequisite for life. Hence, the case for life on Mars at present or at least in the past has been greatly strengthened by Curiosity’s explorations, experiments, and measurements. Following are some of the individual studies that have led to the conclusion that Gale Crater once harbored a lake.

Conglomerate rock called “Hottah" after Hottah Lake in Canada's Northwest Territories. Conglomerate is composed of rounded pebbles that had to be formed in running water.

As early as September 27, 2012,NASA scientists announced that Curiosity (rover) found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars. Mars scientists, in a press conference on December 8, 2014, described observations by Curiosity rover that show Mars' Mount Sharp was made by sediments deposited in a large lake bed over tens of millions of years. This finding suggests the climate of ancient Mars could have been conducive to long-lasting lakes at many places on the Planet. Many scientists had suggested this long ago. There is a long list of where lakes may have existed in the distant past. Rock layers in Gale imply that a huge lake was filled and evaporated many times. Many deltas stacked upon each other support this contention.

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  This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

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  Rock layers in the Murray Buttes area in lower Mount Sharp

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  Rock layers in the Murray Buttes area in lower Mount Sharp

Simulated view of past lake in Gale Crater

After more observations, on October 8, 2015, a large team of scientists confirmed the existence of long-lasting lakes in Gale Crater. The team came to this conclusion based on evidence of old streams with coarser gravel in addition to places where streams appear to have emptied out into bodies of standing water. If lakes were once present, Curiosity would start seeing water-deposited, fine-grained rocks closer to Mount Sharp. That is exactly what was observed. Finely laminated mudstones were discovered by Curiosity; this lamination represents the settling of plumes of fine sediment through a standing body of water. Sediment deposited the Gale Crater lake formed the lower portion of Mount Sharp, the mountain in Gale crater. Research presented in 2018 at the Geological Society of America Annual Meeting in Indianapolis, Indiana explained evidence for huge floods in Gale Crater. Of great significance was a conglomerate rock unit with particles up to 20 centimeters across. To create such a type of rock, water must have been 10 to 20 meters in depth. Between 2 million years to 12,000 years ago, Earth experienced these types of floods. Conglomerate is a rock composed of rounded rocks of various sizes. Rounded rocks are produced by traveling down streams. In the streams they become rounded by hitting the steam bottom and each other. Besides physical evidence of water, there was much more supporting signs of water that was detected by various instruments on Curiosity. Although some are subtle and complicated, they are consistent with a history of water. For instance, many minerals require water for their formation. Many of these types of minerals are in Gale Crater. Curiosity was able to even examine small veins and determine their composition which often turned out to be different than the surrounding rocks. Veins form when fluids move through cracks in rocks.

Researched published in nature Geoscience in October 2019, described how Gale crater underwent many wet and dry cycles as its lake waters disappeared. Sulfate salts from evaporated water showed that pools of salty water once existed in Gale Cater. These ponds could have supported organisms. Curiosity found magnesium sulfate salts which means that the lake must have almost totally evaporated because this salt does not crystalize out from a water solution until nearly all the water has evaporated. The remaining pools of water would have been very salty--such lakes on Earth contain organisms that are salt tolerant. These minerals were found along the edges of what were lakes.

Researchers who examined halos concluded that much water remained in the ground after the lake dried up. Microbes may have been able to live there much longer than was previously believed. The halos represent the tops of large subsurface networks that once held water. Curiosity's instruments found the halos to contain opal. Opal is rich in water which can be obtained by just heating. In the future, colonists may be able to use the opal as a source of water. Just two halos that have an area of a square meter could contain one to 1.5 gallons of water in the top foot.

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  Curiosity's laser-firing Chemistry and Camera (ChemCam) here at Garden City found calcium sulfate in some veins and magnesium sulfate in others. Some veins contained fluorine or varying amounts of iron.

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  Veins Veins form when fluids move through cracks in the rock. They are exposed here because erosion has removed the softer rock that the veins were in.

Some of the more indirect findings are mentioned below. Signs of mineral hydration, probably hydrated calcium sulfate, were reported by NASA on March 18, 2013, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock plus in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock. Minerals that are hydrated needed water to become hydrated, so finding hydrated minerals means that water must have been present. By the start of 2016, Curiosity had detected seven hydrous minerals. The minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. Note that all of these minerals must have formed in water.

Rocks layers from the “Kimberley” formation Layers like this are usually formed under water.

Scientists found manganese oxides in mineral veins in the "Kimberley" region of Gale Crater by using Curiosity's laser-firing device (ChemCam). These minerals need lots of water and oxidizing conditions to form; therefore, this finding points to a water-rich, oxygen-rich past. A study of types of minerals in veins found that evaporating lakes were extant in the past in Gale crater. The Sheepbed Member mudstones of Yellowknife Bay (YKB) were investigated in this research. In January, 2017, JPL scientists announced the discovery of mud cracks in Gale Crater. Such mud cracks form with the aid of water. Analysis using data from the rover’s Dynamic Albedo of Neutrons (DAN) scientists acquired evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 2 feet (60cm), between the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain. Mars even has liquid water at times according to measurements made by Curiosity. Since the humidity goes to 100% at night, salts, similar to calcium perchlorate, will absorb water from the air and make brine in the soil. This manner in which a salt absorbs water from the air is called deliquescence. Liquid water results even though the temperature is very low because salts lower the freezing point of water. We use this idea to melt snow/ice by spreading salt on roads. The liquid brine produced in the night at Gale Crater evaporates after sunrise. Higher amounts of liquid water are expected in higher latitudes where the colder temperature can result in higher levels of humidity more often. Researchers cautioned that the amount of water was not enough to support life; however, it could allow salts to move around in the soil. The brines would occur commonly in the upper 5 cm of the surface, but there is evidence that the effects of liquid water can be detected down to 15 cm. Chlorine-bearing brines are corrosive; therefore design changes may need to be made for future landers.

Ripple marks in Gale Crater that show water was there.

NASA released a picture in February 2023 that shows strong evidence for water. "This is the best evidence of water and waves that we've seen in the entire mission," said Ashwin Vasavada, Curiosity's project scientist at NASA's Jet Propulsion Laboratory in Southern California. These kind of ripple marks are common on Earth along the seashore or bottom of shallow lakes. In the distant past on Mars, waves on the surface of a shallow lake stirred up sediment at the lake bottom to form rippled textures.

Hexagon ridges found in Gale crater show that liquid water may have existed for a long time and not just when an impact or volcano erupted. To make the ridges the ground must have gone through many cycles of water saturating the surface and then drying. Water that developed from the heat of an impact or volcanic process may have persisted for thousands of years, but would not have undergone wet and dry cycles.The ridges were joined at Y-junctions that made hexagonal shapes. Calcium-sulfate and variable magnesium-sulfate were detected in the ridges. These chemicals were deposited by mineral-rich fluids. Originally, there were cracks and then fluids carrying dissolved minerals entered and deposited minerals. Those minerals hardened such that they were harder than the surrounding rock. Later, when erosion took place, ridges were exposed, as they did not erode as much as the surroundings.

File:Mudcracksgale.jpg

Hexagonal ridges formed by mineral-rich water moving through cracks. These are evidence for water lasting a long time.

This discovery is significant. Much evidence exists to show that impacts and volcanic activity could melt ground ice to make liquid water. However, that water may not last long enough for life to develop. This new finding shows here it is not the case–water stayed for some time as it cycled to near dryness at times. For an impact or volcanic activity the water would stay around for thousands of years, but would not show seasonal cycles. Also, with water coming and going there is a better chance of more complex organic compounds being produced. As water evaporates chemicals are concentrated and have a better chance of combining. For example when amino acids are concentrated they are more likely to link up to form proteins. Likewise, nucleotides can form from ribose and phosphate when enriched in small volumes of water. And then RNA and DNA can be created.

Radiation levels

Measurements of radiation levels are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long conceivable organic biosignatures can be preserved. Astronauts on Mars would need to spend most of their time underground for protection from radiation. Future colonies would probably be in lava tunnels; Mars has an abundance of volcanoes, so lava tunnels may be common. Also, perhaps in the future we may have developed robotic earth movers which could move dirt around for cover.

Curiosity took accurate readings of radiation on the way to Mars as well as on the surface. The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. This study estimates that a one-meter depth drill is necessary to access possible viable radioresistant microbe cells. The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these quantities, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. One Sievert exposure is associated with a five percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is three percent. Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.

Measuring the radiation levels, Curiosity finds no stronger radiation on the Martian surface than in low Earth orbit, where the ISS is. This seems the result of Mars' atmosphere deflecting parts of the cosmic rays. This is very good news as it simplifies significantly the construction of living quarters for the settlers. However, the intensity of solar flares still needs to be measured.

The origin of Cosmic rays are not greatly understood. Most are small atomic particles, but some are the nuclei of heavier atoms. They are a major concern in space because they can damage living cells and electronics. The Earth’s atmosphere and magnetic field protect us from their effects. However, they are a potential problem on Mars which has only a very thin atmosphere and no magnetic field. A small number of cosmic rays can have about 40 million times the energy of particles accelerated by the largest particle accelerators. The energy of the most powerful cosmic rays is equal to a baseball moving at 56 mph (90 km/hr.)

Methane

There have been sporadic detections of methane in the Martian atmosphere. Methane can be given off by living organisms; therefore, methane may be an indication of life on Mars. On the other hand, there are other ways of getting methane—ones that do not involve biology. Still this gas should be looked into. Curiosity, at first found no methane, but later found that its level goes up and down.

NASA announced in December 2014 that Curiosity had detected sharp increases in methane four times out of twelve during a 20-month period with the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars instrument (SAM). Methane levels were ten times greater than usual. Because of the temporary nature of the methane spike, scientists think the source is localized. The source may be biological or non-biological.

Methane contains 4 hydrogen atoms and 1 carbon atom covalently bonded to each other. Methane has been detected on Mars, and it could come from living organisms.

After two full Martian years (five Earth years) of measurements, researchers found that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. However, it must be noted that methane levels rise and fall with the seasons, going from 0.24 ppb in winter to 0.65 ppb in summer. They also observed some relatively large methane spikes, up to about 7 ppb, at random intervals. The existence of methane in the Martian atmosphere is exciting because on Earth, most methane is produced by living organisms. Methane on Mars does not prove that life exists there, but it is consistent with life. Ultraviolet radiation from the sun destroys methane; hence, methane doesn’t last long. To explain its presence something must have been creating or releasing it

Organic Chemicals

Curiosity cannot find and was not designed to find alien life on Mars. But, it has the capacity to look for and identify some organic chemicals. Organic chemicals are associated with life. But one must be aware that a certain amount of organic chemicals are expected on the surface due to the arrival of meteorites over billions of years. Some types of meteorites are loaded with a variety of organic chemicals.

Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.

The first major testing of the Martian soil yielded interesting results. On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. The presence of perchlorates in the sample seems highly likely. The presence of sulfate and sulfide is also likely because sulfur dioxide and hydrogen sulfide were detected. Small amounts of chloromethane, dichloromethane and trichloromethane were detected. The source of the carbon in these molecules is unclear. Possible sources include contamination of the instrument, organics in the sample and inorganic carbonates. Perchlorates, first discovered by the Phoenix mission can complicate the measurement of organic chemicals. Perchlorates may destroy organic chemicals.

Map showing the first 14 drill sites Some important locations are labeled.

In a series of six articles in the journal Science December 9, 2013, teams of NASA researchers described, many new discoveries from the Curiosity rover including possible organics that could not be explained by contamination. Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.

Yellowknife Bay with "Snake River" Sheepbed mudstone which contains organic chemicals is found in this location. “Yellowknife” is a town in Canada. The oldest rocks in North America can be found there.

Because much of the carbon was released at a relatively low temperature in Curiosity’s Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. Carbonates are expected when there is water and carbon dioxide present. Both were probably abundant in the past on Mars. The carbon could be from organisms, but this has not been proven. This organic-bearing matter was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called "Snake River." The samples were named ”John Klein” and “Cumberland.” Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.” Later, after further analysis, a team of researchers on December 16, 2014 explained their conclusions that organic compounds have been found on Mars. The compounds were found in samples from drilling into Sheepbed mudstone. Chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane were discovered in the samples.

Location of Sheepbed mudstone where organic chemicals were found. White X is about 43 feet (13 meters) higher in elevation than the Sheepbed-Gillespie contact and at a distance of about 780 feet (240 meters).

At a June 2018 press conference it was announced the detection of more organic molecules in a drill sample analyzed by Curiosity. Some of the organic molecules found were thiophenes, benzene, toluene, and small carbon chains, such as propane or butane. The identity of all the chemicals were not all resolved. At least 50 nanomoles of organic carbon are still in the sample, but were not specifically determined. The remaining organic material probably exists as macromolecules organic sulfur molecules. Organic matter was from lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, by the Sample Analysis at Mars instrument suite.

In late June, 2022, NASA announced the amount of total carbon found in early samples at Gale Crater. At least 200 to 273 parts per million of organic carbon was measured. This level of organics is comparable to or even greater than the amount found in rocks in some locations on Earth, such as in the Atacama Desert This amount is even more than found in Mars meteorites. Organic cemicals are evidence that Mars could have had life, but organic carbon can also come from nonliving sources, such as meteorites, volcanoes, or be formed in place by surface reactions.

Minerals and Rocks of Mars

With a complex of instruments on Curiosity, we were able to determine a great deal more about the geological make-up and history of Mars. Many, may rocks and soil samples were analyzed by various devices. Basically, we understand Mars as being mostly made of volcanic materials, especially the dark rock basalt which comes out of volcanoes. Mars has many huge volcanoes so this is to be expected. We also found that many of the minerals that weather from basalt. By studying these minerals we can arrive at conclusions about the past conditions that produced them. Many of the minerals were hydrated. That means that water was around. Some of the minerals are clay minerals; clay minerals are significant because not only do they need lots of water to form, but they can’t develop in acid conditions. So, in summary the examinations of rocks/minerals show that Gale Crater contained a lake for a long time with a near neutral pH. It was neither acid or alkaline. The lake had water that could support life. On Earth some organisms have evolved to live in an acid environment, but the vast majority of Earth organisms live in liquids with a near neutral pH. Our stomachs secrete strong hydrochloric acid—not just to digest our foods, but the acid kill things that found there way into our stomachs.

Besides basaltic minerals and their weathered products, Curiosity found what are called more evolved rocks. The minerals in these rocks were formed by various processes underground. These are significant because many of our useful mineral ores we use on Earth are from these more evolved minerals. We will understand much more of the history and deep structure of Mars when we receive data from instruments on the InSight Mission. It will use a seismometer and a heat probe. It landed in late November 2018 in the Elysium quadrangle. What follows are some of the studies that came from Curiosity’s probes of rocks. On October 17, 2012, at Rocknest (Mars), the first X-ray crystallography and of Martian soil was performed. The outcomes of this test revealed the presence of feldspar, pyroxenes and olivine. Martian soil was like the weathered basaltic soils of Hawaii Volcanoes. The sample was composed of dust distributed from Martian dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.

”Jake Matijevic rock, the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on Curiosity It is alkaline and relatively fractionated; hence, it is different than most other rocks on Mars. On Earth we get many valuable minerals from fractionated rocks. Marks show where instruments analyzed it.

In the journal Science from September 2013, researchers explained a different type of rock called "Jake M (rock)" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the Curiosity rover, and was different from other known Martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Fractionated rocks form as magma cools in large magma chambers. In those chambers some minerals float to the surface; others sink due to a higher density. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes). French and U.S. scientists found a type of granite after studying images and chemical results of 22 rock fragments. The composition of the rocks was resolved with the ChemCam instrument. These pale rocks are rich in feldspar and may contain some quartz. The rocks are similar to Earth's granitic continental crust. On Earth these kinds of rocks form deep underground and are later exposed by erosion. By landing in Gale crater, Curiosity was able to sample a variety of rocks because the crater dug deep into the crust, thus exposing old rocks, some of which may be about 3.6 billion years old. For many years, Mars was thought to be composed of only the dark, igneous rock basalt, so this is a significant discovery. As of 2018, Curiosity's CheMin has discovered discovered olivine, pyroxene, feldspar, quartz, magnetite, iron sulfides (pyrite)and pyrrhotite), akaganeite, jarosite, and calcium sulfates (gypsum, anhydrite, basanite)

Life was possible in Gale Crater

The aim of the Curiosity Rover was not to find alien life, but it was able to find things that could lead us to believe that life may have been possible in Gale Crater Of course, a major case for life would have been to find evidence of past water. Finding out that the water could have a suitable pH is another big plus. Our rover did indeed find evidence for the right kind of water in the past. Various chemicals we think our necessary for life and for the development of life. Curiosity has found many of these as well. Many theories about the origin of life involve clay minerals. Clay particles are thin and flat; hence, they have a high surface area. Chemicals can attach to clay particles and react with other chemicals that are also stuck on the surface of the clay. Curiosity has found clay. In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide.

Drill hole that went into rock called “John Klein.” Chemicals detected in this sample showed that this spot was suitable for microbial life.

Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals. Some samples were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species. These types of iron and sulfur could have been used by living organisms. Some clays presented a relative young age (Late Noachian/Early Hesperian or younger age); consequently, in this location neutral pH lasted longer than previously thought. Finding clay minerals is significant because to be created they need a near neutral pH and the water needs to be around for a good length of time. CheMin found feldspar, mafic igneous minerals, iron oxides, crystalline silica, phyllosilicates, sulfate minerals in mudstone of Gale Crater. Some of the trends in these minerals at different levels suggested that at least part of the time the lake had near-neutral pH. This finding of more evidence that the lake in Gale Crater probably had a neutral pH gives much support to life thriving there. On March 24, 2015, a paper was released describing the discovery of nitrates in three samples analyzed by Curiosity. The nitrates are believed to have been created from diatomic nitrogen in the atmosphere during meteorite impacts. Nitrogen is necessary for all forms of life because it is used in the building blocks of larger molecules like proteins, DNA, and RNA. Nitrates contain nitrogen in a manner that can be used by living organisms; nitrogen in the air cannot be used by organisms. This discovery of nitrates adds to the evidence that Mars once could have had life. Researchers in December 2016 announced the discovery of the element boron by Curiosity in mineral veins. For boron to be present there must have been a temperature between 0–60 degrees Celsius and a neutral-to-alkaline pH. The temperature, pH, and dissolved minerals of the groundwater support a habitable environment. So, boron is a marker for an environment conducive for life. Of great significance is that boron has been suggested to be necessary for life to form. Its presence stabilizes the sugar ribose which is an ingredient in RNA. Specifics of the discovery of Boron on Mars were described in a paper written by a large number of researchers and published in Geophysical Research Letters. By 2018, researchers had concluded that Gale Crater has experienced many episodes of groundwater. As this was going on the chemistry of the groundwater changed. These chemical changes were the kind that would support life.

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  Mud cracks appearing as a network of ridges, as seen by Curiosity Rover.

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  Silica-rich halos Geologists maintain that the silica in the halos went from older to younger young with the aid of groundwater. Scientists concluded that groundwater must have been present for a long time here.

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  Fractures that went through both Murray mudstone and Stimson sandstone layers had silica deposited in them (shown in left drawing). After erosion removed most of Stimson layer, halos were found around the fractures by the Curiosity Rover. Because the Stimson was formed after the lake disappeared, water must have been in the ground for a long time after the lake dried up.

Flower-like Concretion

In the spring of 2022, pictures were circulated of a small feature imaged in Gale Crater by Curiosity that resembled a fossil. It was a type of concretion. That is it is a mineral formation that formed by minerals precipitating from water. Water going through the ground dissolves minerals. These minerals can then be deposited around a nucleus. The resulting structure will be harder than the ground around it. When erosion removes the softer ground, the structure (called a concretion) will remain.

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  Concretions discovered by Curiosity in Gale Crater. the one that looks like a flower is called "Blackthorn."

Carbon 12

                            One place where Curiosity measured Carbon 12 levels suggestive of life

Evidence of life on Mars was published on January 19, 2022. The study was carried out with measurements made by the Curiosity Rover which is exploring Gale Crater. Rover’s Tunable Laser Spectrometer (TLS) determined the abundance of carbon Isotopes in 24 samples. In many of the samples the relative amount of carbon 12 compared to carbon 13 suggested organisms altered the relative amounts of the isotopes. Living things incorporate more carbon 12 than carbon 13 in organic compounds. If we find more carbon 12 than expected, organisms may be the cause. Some of the results are what one would see in Australia from 2.7 billion year old sediment. The carbon 12 there was produced when methane was consumed by mats of microorganisms.

Each atom of carbon in the universe contains 6 particles, called protons. However, carbon atoms can contain different numbers of other particles, called neutrons. Most carbon contains 6 neutrons, but a certain percentage contain 7 or 8. Carbon 12 has 6 protons and 6 neutrons—that is the one mostly used by organisms. Many have heard of carbon 14. It does not exist very long and is used in dating things from the past.

Carbon 12 and carbon 13 are both stable, that is they do not change as time passes. On the other hand, carbon-14 is unstable and changes over precise periods of time. It has a half-life of 5,730 ± 40 years, so it is measured to date things. In 5,730 years half of it changes to nitrogen by throwing off an electron (Beta particle.) And then in 5,730 years another half changes to nitrogen. And this process continues until all the carbon is gone. Most of the carbon-14 on Earth comes from the action of cosmic rays on nitrogen in the atmosphere. But some has come from the nuclear tests between 1955 and 1980.

The samples that showed lower levels of carbon 13 then expected (maybe because of biology) were found in five locations over a nine year span, from August 2012 to July 2021. They include the Yellowknife Bay, Bagnold dunes, and Vera Rubin ridge (VRR). These different locations include a variety of materials--mudstone, sand, and sandstone.

Although life could have produced the observed carbon ratios, other possibilities exist. Mars may have passed through a giant cloud containing an excess of carbon 12. Furthermore, the cloud could have lowered the temperature on Mars and caused the lighter carbon to settle on Mars glaciers. Our solar system passes through these clouds about every few hundred million years. Another possible mechanism is that ultraviolet light (UV) could have reacted with carbon dioxide in the Martian air to produce organic compounds. The third possibility is organisms creating methane that is enriched in carbon 12. The methane, a gas, would be converted to organic compounds in the air by UV, and then land on the ground. This study suggests the existence of life on Mars, but it would nice to find some complex organic molecules like proteins, fats, enzymes, or nucleic acids (DNA, RNA) that are closely associated with living process, but none have so far been found. Also, small items that look like fossils would be the icing on the cake to scientists.

Meteorites

Using date gathered with Mastcam, a team of researchers found what they believe to be iron meteorites. These meteorites stand out in multispectral observations as not having the usual ferrous or ferric absorption features as the surrounding surface. One would expect to find many meteorites on the Martian surface because of billions of years of bombardment by asteroids of various sizes. Both the Spirit and Opportunity rovers on Mars found meteorites. Meteoritic material may be very important for future colonists on the Red Planet. We may invent robotic machines to go out and collect and process iron meteorites.

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  Gray, golf ball-sized iron-nickel meteorite Type of meteorite was determined with laser pulses. Light lines are mineral veins. Meteorite was named “Egg Rock.”

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  Close view of Egg Rock The small white spots are where the laser hit it. Analysis with laser data showed it was an iron-nickel meteorite.

Astronomy Observations

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  Eclipse of the sun by the Mars moon Phobos

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  Sunspots and the planet Mercury passing in front of sun

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  Planets, moons stars, asteroids, as seen by Curiosity

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  Earth and Moon, as seen from Mars by Curiosity

Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.

Regolith for greenhouses

The Martian regolith resembles basaltic soil from Hawaii.

Conclusion: The regolith is a good base for making soil for greenhouses in the Martian colony.

Future

Since Curiosity is powered by radioactive isotopes, rather than solar panels, it may be exploring Mars for many, many years. About the only major potential problem in sight are the wheels. Fairly early on in the mission, it was noticed that the wheels had been punctured by sharp rocks. When driving over certain surfaces, Curiosity’s wheels were being pierced by sharp rocks sticking up. These rocks from hell were probably part of the underlying rock formation; as such they did not give, even when the one ton rover passed over them. The wheels have parts that are very thin—those are the ones being affected by sharp rocks. Still, the people in charge of driving the rover are being very careful.

Curiosity Trivia

Bobak Ferdowsi, a young man in the control room for Curiosity, became popular with ladies after they saw him at his computer during the landing. He had a prominent Mohawk and received hundreds of marriage proposals via Twitter.

See Also

• Oceans on Mars
• Rivers on Mars

Recommended reading

• Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.

• Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>
• Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.

External links

• [ https://www.youtube.com/watch?v=LAL4F6IWC-Y Full Video of Curiosity Landing on Mars]
• [ https://www.youtube.com/watch?v=zqhK8dA7iO8 Five Years of Curiosity on Mars (public talk)]
• [ https://www.youtube.com/watch?v=3Z9zgMOjdPE The Curiosity Rover's Most Amazing Discoveries]
• [ https://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf Press kit for Curiosity]
• [ https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf Press Kit for Mars Science Laboratory launch]
• Mars Global Surveyor Shows landing sites on a rotating globe

• 360 Video: Curiosity Rover Departs Vera Rubin Ridge