In people's minds, Mars has always been a beautiful Red Planet. However, recent photos sent back by the Perseverance Mars rover show that red is not its only color, covering many surface rocks with a mysterious purple substance.
Two holes can be seen where Perseverance uses a robotic arm to drill rock samples
Image source: NASA, JPL-CALTECH
Ann Ollila, a geochemist at Los Alamos National Laboratory, presented a preliminary analysis of these purple coatings at a recent meeting of the American Geophysical Union (AGU): The purple material appears to form a thin, smooth coating on the surface of some rocks, while on others it shows traces like spots splashed by painting pigments. There are also rocks that look like they are covered in purple-red frost.
The Perseverance Mars rover captured this image of the rock in May 2021, with purple material visible on the right side of the frame and five small holes arranged on the rock surface.
This mysterious purple substance meanders freely on the surface of the rock, forming points, lines, and surfaces of different sizes and shapes. How did they come about? There is no definitive answer yet.
Scientists hope to uncover more mysteries. Nina Lanza, head of the space and planet exploration team at Los Alamos National Laboratory, has been working with Orilla on this mysterious coating. She believes that by studying the "code" of chemicals or minerals to the surrounding environment when the coating is formed, it is possible to reconstruct the historical environment of Mars that has long since disappeared. So, the origin of these mysterious purple substances is likely to be a clue to the mysteries of Mars. In addition, analyzing the presence of microbes on the surface of rocks can also help scientists find evidence of life.
Jezero Crater was once an ancient lake formed billions of years ago by meteorite impacts. Inside the 28-mile-wide pit, purple mysterious substances can be seen everywhere. The plaques make scientists scratch their heads. Bradley Garczynski of Purdue University studied this coated substance through images taken with a Mask-Z camera. The camera uses a variety of filters to block light at specific wavelengths, and scientists can get a rough idea of the rock's composition.
Meanwhile, Orila and colleagues are using the SuperCam instrument on perseverance to study the coating in more depth. SuperCam can fire lasers at rocks, vaporize a small piece of material, and extract its elemental composition. With a clicking sound, each laser emission also leaves a small pit in the surface. Microphones on the rover record the noise of the machine's operation, which scientists can hear as the laser penetrates the coating. These sound sides reveal certain properties of the rock, such as hardness.
These preliminary analysis results show that the purple material on the surface of the rock appears to be softer and has different chemical properties than the rock below. Images of Mastcam-Z suggest that the coatings may contain iron oxide, while SuperCam shows they are rich in hydrogen, along with some magnesium.
The presence of hydrogen suggests that these purple plaques may contain water. And the presence of iron oxides, rust, also points to water. The next step in research could shed light on the Red Planet's wet past, including how long the water stayed in Jezero Crater and perhaps the chemical properties of the vanished lake itself.
Generally speaking, on Earth, the soft layer of rock surface is usually associated with life. The nooks and crannies of rocks can create a small safe haven for microbes in harsh environments, sheltering them from the wind and rain and providing them with nutrients. In the process of metabolism, some metal materials will be deposited on the surface of the rock, leaving traces. If this relationship holds true on Mars, then studying this surface material can find evidence of the presence or absence of microorganisms.
In addition to the purple material, the Curiosity rover also discovered a manganese-rich black surface material at Gale Crater. The discovery is reminiscent of a special coating on Earth known as "varnish," which is often teeming with microbes. Chris Yeager, an environmental microbiologist at Los Alamos National Laboratory, said that in a recent survey of "varnishes" across the United States, scientists discovered "radiation-resistant bacteria" — a special type of cyanobacteria that allows manganese to concentrate to prevent the destruction of solar radiation, like applying a layer of "sunscreen."
So far, the team has only analyzed a small sample, and they still face many challenges. For example, the different chemical readings recorded by SuperCam and the changes in laser sound do not always seem to be consistent; it is complicated to separate the purple coating, rocks and Martian dust from each other; strong winds on Mars always interfere with the sound emitted by laser operations, and so on.
In addition, the location of the purple plaque in the crater is also confusing. Perseverance's route did not pass through lake sediments, but through rocks formed by cooling magma. How did the rock get to its current position at the bottom of the pit? How do I get in touch with water? None of this has yet been answered.
So, when Perseverance made the long journey to Jezero's Delta, the team was excited to continue the study. The Jezero Delta is an alluvial fan formed by ancient rivers flowing into the crater. Perhaps, some secrets can be solved here.
Deciphering Mars is not easy. Bringing these rocks back to Earth for laboratory analysis is one of the few viable ways. At present, the Martian rock samples sampled by Perseverance are sealed and preserved for future return to Earth. Although these mysterious purple substances are fragile, the research team still hopes that some of these samples will withstand the "ravages" of the sampling process and survive intact. In this way, in the near future, scientists can study these relics from Mars up close and closer.
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https://www.nationalgeographic.com/science/article/mysterious-purple-coating-found-on-mars-rocks