화성에서 온 사진 한 장...이번엔 진짜 물인가? VIDEO: Liquid water 'lake' revealed on Mars

Liquid water 'lake' revealed on Mars

By Mary Halton

Science reporter, BBC News

25 July 2018

NASA/JPL/MALIN SPACE SCIENCE SYSTEMS Image caption

The proposed lake sits beneath ice near the south pole of Mars

화성에서 온 사진 한 장...이번엔 진짜 물인가?

화성 남극에서 호수가 발견했다

이탈리아 연구진, 얼음 아래서 소금물 호수 찾아

이탈리아 연구진들이 화성 남극의 얼음 덩어리 아래에서 호수가 있다는 강력한 증거를 발견했다고 IT매체 씨넷이 25일(현지시간) 보도했다.

이탈리아 국립천체물리연구소(INAF) 연구진들은 유럽우주국(ESA)의 화성탐사선 ‘마스 익스프레스’에 탑재된 레이더 탐사장비인 마시스(MARSIS)가 수집한 자료를 분석해 화성 얼음 층 1.5km 아래에 폭이 20km이나 되는 거대한 소금물 호수가 있다는 사실을 발견했다.

연구진들은 이 곳의 레이더 신호가 다른 곳과 크게 달라지는 것을 확인한 후, 그 원인을 찾기 위해 수 년간 조사를 계속해 왔다.

마시스(MARSIS)는 전자기파를 화성 지표면을 향해 쏜 다음 돌아오는 파장을 분석해 지하의 상태를 추정한다. 이때 땅이나 얼음 등은 전자기파가 잘 통과하지만, 금속이나 물에서는 튕겨져 나오게 되는데, 연구진들은 이 곳에서 전자기파가 강하게 튕겨 나오는 것을 발견한 것이다.

국제천문연맹(IAU)의 로베르토 오로세이(Roberto Orosei)는 “이런 강력한 신호는 다른 설명이 있을 수 없다”며, "화성에 물이 있다고 결론 내렸다."고 밝혔다.

해당 연구결과는 국제학술지 ‘사이언스’에 실렸다. 연구진들은 이 호수가 얼마나 깊은 지는 정확히 알 수는 없지만 최소 1미터 이상이라고 추정했다.

이 지역의 표면 온도는 영하 30℃ 정도지만, 높은 염분 함량으로 인해 얼지 않고 녹아 있다고 오로세이 박사는 밝혔다. 지구에도 남극 및 그린란드 빙상 밑에 이와 비슷한 수냉 호수가 있다.

이정현 기자 / jh7253@zdnet.co.kr

황기철 콘페이퍼 에디터 큐레이터

Ki Chul Hwang, conpaper editor, curator

"It's probably not a very large lake," said Prof Roberto Orosei from the Italian National Institute for Astrophysics, who led the study.

Marsis wasn't able to determine how thick the layer of water might be, but the research team estimate that it is a minimum of one metre.

"This really qualifies this as a body of water. A lake, not some kind of meltwater filling some space between rock and ice, as happens in certain glaciers on Earth," Prof Orosei added.

Image copyrightESA/INAF

Artists' impression: Mars Express probing the planet's surface. Marsis radar results above.

How was it found?

Radar instruments like Marsis examine the surface and immediate subsurface of the planet by sending out a signal and examining what is bounced back.

The continuous white line at the top of the radar results above marks the beginning of the South Polar Layered Deposit; a filo pastry-like accumulation of water ice and dust.

Beneath this, researchers spotted something unusual 1.5km under the ice.

"In light blue you can see where the reflections from the bottom are stronger than surface reflection. This is something that is to us the tell tale sign of the presence of water," says Prof Orosei.

Artists' impression: Marsis data shows an area of high reflectivity (dark blue) which is thought to be water

What does this mean for life?

Nothing definitive. Yet.

Dr Manish Patel from the Open University explained: "We have long since known that the surface of Mars is inhospitable to life as we know it, so the search for life on Mars is now in the subsurface.

"This is where we get sufficient protection from harmful radiation, and the pressure and temperature rise to more favourable levels. Most importantly, this allows liquid water, essential for life."

This principle of following the water is key to astrobiology - the study of potential life beyond Earth.

So while the findings suggest water is present, they don't confirm anything further.

"We are not closer to actually detecting life," Dr Patel told BBC News, "but what this finding does is give us the location of where to look on Mars. It is like a treasure map - except in this case, there will be lots of 'X's marking the spots."

Image copyrightSCIENCE PHOTO LIBRARY

Astrobiologists study extreme environments like salt lakes on Earth to understand how life might survive on Mars

The water's temperature and chemistry could also pose a problem for any potential martian organisms.

In order to remain liquid in such cold conditions (the research team estimate between -10 and -30 Celsius where it meets the ice above), the water likely has a great many salts dissolved in it.

"It's plausible that the water may be an extremely cold, concentrated brine, which would be pretty challenging for life," explained Dr Claire Cousins, an astrobiologist from the University of St Andrews, UK.

What next?

While its existence provides a tantalising prospect for those interested in the possibility of past or present life on Mars, the lake's characteristics must first be verified by further research.

"What needs to be done now," explained Dr Matt Balme from the Open University, "is for the measurements to be repeated elsewhere to look for similar signals, and, if possible, for all other explanation to be examined and - hopefully - ruled out.

"Maybe this could even be the trigger for an ambitious new Mars mission to drill into this buried water-pocket - like has been done for sub-glacial lakes in Antarctica on Earth," he added.

Image copyrightSCIENCE PHOTO LIBRARY

The area has been compared to Lake Vostok, which lies 4km beneath the Antarctic ice

Scientists have previously claimed to find bacterial life in the buried depths of Antarctica's Lake Vostok, but drilling on Mars would make for an ambitious project indeed.

"Getting there and acquiring the final evidence that this is indeed a lake will not be an easy task," said Prof Orosei.

"It will require flying a robot there which is capable of drilling through 1.5km of ice. This will certainly require some technological developments that at the moment are not available."

The findings were reported in Science.

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https://www.bbc.com/news/science-environment-44952710

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