A radar map of the Martian north pole reveals a four-layer ice structure laid down over a period of five million years. The ice structure is on top of sedimentary rocks hundreds of kilometers thick, scientists said earlier this month in a report.
The data was provided by NASA’s Mars Reconnaissance Orbiter. It provides ground-breaking insight into the formation of the Martian ice cap and the “thermal history” of the red planet, said Roger Phillips of Southwest Research Institute in Boulder, Colorado, US.
PHOTO: AP
Researchers found that the polar cap is formed by up to four layers of ice rich in sand and dust, separated by clearer sheets of ice. They believe the structure of the polar cap is the result of variations in Mars’ orbit over the years. One Martian year equals 1.88 Earth years.
The ice layers were accumulated over a period of about five million Earth years, said the scientists in a paper published in Science.
The radar images also show that the underlying sedimentary rocks have not been deformed by the enormous weight of the ice cap, suggesting that the Martian crust in the area is more than 300km thick.
The radar mapping of the polar cap also allows scientists to track the movement of dust over the Martian landscape over the years, researchers said.
The Martian north pole is part of a vast sedimentary plain built up over more than three billion years from ice erosion deposits, dust, volcanic lava and other sundry materials.
(AFP)
本月稍早科學家在一份報告中表示，從火星北極傳回來的雷達影像顯示，該地有超過五百萬年之久的四層凍土層，而凍土層的下方是厚達數百公里的沉積岩層。
美國科羅拉多州波德市西南研究所的羅傑．飛利浦斯說，美國航太總署的火星偵察軌道器回傳的這些前所未見的照片，讓人類可以一窺這顆紅色星球的「熱歷史」，及其冰帽結構。
研究學家發現，北極極冠是由四層富含沙塵的冰層組成，層間則被更清純的冰層分隔。科學家認為，北極極冠會出現這樣的結構，是火星經年軌道變遷的結果。火星上的一年，約等於地球上的一點八八年。
科學家在發表於《科學》雜誌的文章中指出，這些凍土層是經過約五百萬年（地球年）沉積而成。
這些雷達影像也顯示，下層的沉積岩並沒有被極重的冰帽壓到變形，這意味著火星該區地殼的厚度超過三百公里。
研究人員表示，科學家也能透過火星極冠的雷達影像，來追蹤這幾年火星地貌改變的情形。
三十多億年來，冰蝕沉積物、 塵土、火山熔岩和其他各式各樣的物質，在火星上沉積成一片遼闊的平原，而火星北極就是其中一部分。
（法新社�翻譯：袁星塵）
Photographer Franziska Stuenkel likes to take spontaneous urban shots, so she needs a nimble camera that is ready to go when inspiration strikes: her German-made Leica M11. “I have to be very quick and discreet,” said the Berlin-based artist who captures reflections of people walking past windows, their contours merging with the shapes behind the glass. Stuenkel’s compact Leica is the perfect camera for the job, the 51-year-old told AFP. Famous for its pocket-sized and retro-style devices, the Leica brand is celebrating a milestone as it marks 100 years since its first commercial camera was presented to the public. The
Picture a 45-foot-long animal with a 5-foot-long skull and 3-foot-long arms. It may not seem strange until you realize that a human with those proportions would be 6 feet tall with 5-inch arms. Although the Tyrannosaurus rex went extinct 65 million years ago, the mystery of its unusual body __1__ has fascinated scientists for over a century. Barnum Brown, the paleontologist who first discovered T. rex fossils, initially found it hard to believe that the tiny arms belonged to such a __2__ creature. One of his colleagues speculated that the short forelimbs might have been used to hold the
As global travel rebounds following the COVID-19 pa ndemic, the longstanding issue of overtourism has returned stronger than ever. Throughout 2024, numerous popular destinations worldwide struggled with tourist numbers that far exceeded their infrastructural and environmental capacities. Not only does this surge congest streets and pollute landscapes, but it also endangers cultural sites and disrupts the daily lives of residents. In response to the growing problem of “overtourism,” various nations have adopted diverse strategies, some of which have sparked controversy. Venice, Italy, has not hesitated to take bold action; since 2024, the city has implemented one of the
Dogs’ noses are incredibly keen. They can even detect changes in cortisol levels in human sweat and breath. Known as the “stress hormone,” cortisol increases when humans are under pressure. Recent research indicates that the smell of human stress can influence a dog’s behavior and emotions. In the study, human volunteers were exposed to the stressful tasks of preparing and delivering a speech on the spot and then solving math problems. __1__ Researchers collected sweat and breath samples from the volunteers on pieces of cloth during both their stressful and restful states. Meanwhile, other researchers worked with 18
RSS