Mars’ta Nemli Durumda Depolanma Sürecine Ait İpuçlarına Rastlandı

Amerikalı biliminsanları Mars yüzeyinde karbonat keşfetmeleri, Kızıl Gezegen’de geçmişte bulunduğu tahmin edilen suyun pek de asitli olmadığını ve yaşamın ortaya çıkmasına elverişli bir ortam sağladığını düşündürüyor.

Science dergisinde yayımlanan makaleye göre, Amerikan Havacılık ve Uzay Kurumunun (NASA) Mars’ın yörüngesinde bilimsel çalışmalarını sürdüren Mars Yörünge Kaşifinin (Mars Reconnaissance Orbiter-MRO) spektrometresi sayesinde yaptığı keşif, bu gezegenin sularının, 3,6 milyar yıldan fazla zaman önce mineraller oluşmaya başladığında, nötr bir pH’ı veya alkalini bulunduğu gösteriyor.

Karbonat, Dünya yüzeyinde bolca bulunan ve asitte çabucak çözünen bir mineral. Biliminsanları, Mars yüzeyinde karbonatın varlığının, Kızıl Gezegen’in tarihinde asitli bir çevrenin egemen olduğu yönündeki yaygın teoriye ters düştüğüne işaret ediyor.

Bu çalışmaya katılan biliminsanları, Mars’ta karbonatın bulunmasının, tersine, değişik tipte nemli çevreler bulunduğuna işaret ettiğini ve bu çevrelerin çeşitliliği arttıkça, yaşamın oluşması şansının da arttığını belirtiyorlar.

Araştırmanın başında yer alan Johns Hopkins Üniversitesi uygulamalı fizik laboratuvarından Scott Murchie, çalışmalarının sonunda karbonatın varlığını keşfettiklerini, bunun da kendilerine Mars’ın değişik dönemleri boyunca var olan koşullar konusunda daha fazla ayrıntı sağladığını söyledi.

Four Types of Deposits From Wet Conditions on Early Mars

Each of these four panels shows a close-up view of a different type of geological deposit formed with the involvement of water, based on observations by NASA’s Mars Reconnaissance Orbiter. All four date from the earliest period of Martian history, called the Noachian Period.

The upper-left panel shows carbonates overlying clays in the Nili Fossae region of Mars. The view combines color-coded information from infrared spectral observations by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) with an underlying black-and-white image from the High Resolution Imaging Science Experiment (HiRISE) camera. Beneath a rough-textured capping rock unit (purple) lie banded olivine-bearing layers (yellow), which in some places have been partially or wholly altered to carbonate (green).

The upper-right panel shows phyllosilicates and chlorides in the Terra Sirenum region, observed by CRISM and HiRISE. Medium-toned, finely fractured rocks containing chloride salts either underlie higher-standing, light-toned phyllosilicates or fill in low spots between them. Both sit on dark, eroded volcanic material.

The lower-left panel shows the upper portion of canyon wall in Coprates Chasma, observed by HiRISE and CRISM. The chasm rim cuts across the middle of the image. The wall slopes down to the top of the image and continues outside the region shown, exposing multiple phyllosilicate-bearing layers in a section of rock 7 kilometers (4 miles) thick. Two of the layers shown here are finely fractured aluminum clays that dominate the lower half of the image, underlain by thin beds of iron-magnesium clays at the top of the image. The dark material is a remnant of an overlying layer of basaltic sand that has been partly eroded away by the wind.

The lower-right panel shows phyllosilicates with vertically layered compositions in Mawrth Vallis, observed by HiRISE (presented in enhanced color) and CRISM. The brown-colored knob in the middle of the scene is a remnant of cap rock that overlies aluminum clays (blue-gray), which in turn overlie iron-magnesium clays (buff).

Image credit: NASA/JPL/JHUAPL/University of Arizona/Brown University.

Scientists Find ‘Missing’ Mineral and Clues to Mars Mysteries

Researchers using a powerful instrument aboard NASA’s Mars Reconnaissance Orbiter have found a long-sought-after mineral on the Martian surface and, with it, unexpected clues to the Red Planet’s watery past.

Surveying intact bedrock layers with the Compact Reconnaissance Imaging Spectrometer for Mars, or CRISM, scientists found carbonate minerals, indicating that Mars had neutral to alkaline water when the minerals formed at these locations more than 3.6 billion years ago. Carbonates, which on Earth include limestone and chalk, dissolve quickly in acid. Therefore, their survival until today on Mars challenges suggestions that an exclusively acidic environment later dominated the planet. Instead, it indicates that different types of watery environments existed. The greater the variety of wet environments, the greater the chances one or more of them may have supported life.

“We’re excited to have finally found carbonate minerals because they provide more detail about conditions during specific periods of Mars’ history,” said Scott Murchie, principal investigator for the instrument at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

The findings will appear in the Dec. 19 issue of Science magazine and were announced Thursday at a briefing at the American Geophysical Union’s Fall Meeting in San Francisco.

Carbonate rocks are created when water and carbon dioxide interact with calcium, iron or magnesium in volcanic rocks. Carbon dioxide from the atmosphere becomes trapped within the rocks. If all of the carbon dioxide locked in Earth’s carbonates were released, our atmosphere would be thicker than that of Venus. Some researchers believe that a thick, carbon dioxide-rich atmosphere kept ancient Mars warm and kept water liquid on its surface long enough to have carved the valley systems observed today.

“The carbonates that CRISM has observed are regional rather than global in nature, and therefore, are too limited to account for enough carbon dioxide to form a thick atmosphere,” said Bethany Ehlmann, lead author of the article and a spectrometer team member from Brown University, Providence, R.I.

“Although we have not found the types of carbonate deposits which might have trapped an ancient atmosphere,” Ehlmann said, “we have found evidence that not all of Mars experienced an intense, acidic weathering environment 3.5 billion years ago, as has been proposed. We’ve found at least one region that was potentially more hospitable to life.”

The researchers report clearly defined carbonate exposures in bedrock layers surrounding the 1,489-kilometer-diameter (925-mile) Isidis impact basin, which formed more than 3.6 billion years ago. The best-exposed rocks occur along a trough system called Nili Fossae, which is 666 kilometers (414 miles) long, at the edge of the basin. The region has rocks enriched in olivine, a mineral that can react with water to form carbonate.

“This discovery of carbonates in an intact rock layer, in contact with clays, is an example of how joint observations by CRISM and the telescopic cameras on the Mars Reconnaissance Orbiter are revealing details of distinct environments on Mars,” said Sue Smrekar, deputy project scientist for the orbiter at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

NASA’s Phoenix Mars Lander discovered carbonates in soil samples. Researchers had previously found them in Martian meteorites that fell to Earth and in windblown Mars dust observed from orbit. However, the dust and soil could be mixtures from many areas, so the carbonates’ origins have been unclear. The latest observations indicate carbonates may have formed over extended periods on early Mars. They also point to specific locations where future rovers and landers could search for possible evidence of past life.

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