From European Space Agency via Manu: “Mars and water”


From Manu Garcia, a friend from IAC.

The universe around us.
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[I used Manu’s article and not ESA’s because ESA did not provide an article in English and Manu always has a language choice.]

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Mars Express detects water buried under the south pole of Mars

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Mars Express ESA used radar signals bounced through permafrost for evidence of a water tank buried in the southern polar cap.

ESA/Mars Express Orbiter

Twenty-nine specific observations were made between 2012 and 2015 in the region of Planum Australe at the South Pole using the Mars Advanced Radar for radar subsoil and Ionosphere Sounding, MARSIS instrument. A new mode of operation established in this period allowed the recovery of higher quality data than before the mission.

The study area of ​​200 square km shown in the image on the left and radar traces on the surface are shown in the middle image for multiple orbits. The background image grayscale is an image of System Thermal Emission Imaging Odyssey Mars from NASA and highlights the underlying topography: a plain featureless with escarpments ice cream on the bottom right (south).

Traces are encoded by colors corresponding to the “power” of the radar signal reflected by subsurface features. The large blue area near the center corresponds to the bright main area of ​​the radar, detected in many overlapping orbits of the spacecraft.

Subsurface radar profile is shown in the right panel for one of the orbits of Mars. The characteristic bright horizontally at the top represents the frozen surface of Mars in this region. Laminates deposits south pole, layers of ice and dust, are at a depth of about 1.5 km. Below is a base layer in some areas is even brighter than the surface reflections, highlighted in blue, while elsewhere is quite diffuse. The analysis of the details of the reflected signals from the base layer produces properties corresponding to liquid water.

The bright reflections are centered around 193 ° E / 81 ° S in orbits intersect, delineating a well-defined area 20 km wide.

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Context map copyright: NASA / Viking; THEMIS background: NASA / JPL-Caltech / Arizona State University; MARSIS data: ESA / NASA / JPL / ASI / Univ Rome. R. Orosei and other 2018

NASA THEMIS satellite

The radar data collected by Mars Express ESA indicate the existence of a mass of liquid water under layers of ice and dust in the southern polar region of Mars.

The vast networks of dry river valleys and huge overflow channels probes photographed by circumnavigating the globe realize the aquatic past of Mars. These orbiters, along with Landers and rovers surface also discovered minerals that could only be formed in the presence of liquid water.

However, the climate has changed significantly over the 4,600 million years of history of the planet, and today can no longer be liquid water on the surface, so scientists are searching underground. Preliminary results from Mars Express, which has spent 15 years in operation, have detected water ice at the poles and subsurface layers mixed with powder.

It has long been suspected of the presence of liquid water at the base of the poles; After the, studies on Earth have amply demonstrated that the melting point dela gua decreases under the pressure of a glacier. Furthermore, the presence of salts on Mars could further reduce the melting point of the water and make to remain liquid even at freezing temperatures.

However, testing of advanced radar to investigate the ionosphere and subsurface of Mars, MARSIS, which was the first probe to orbit another planet radar, they were inconclusive … so far.

The insistence of the scientists working with this instrument has allowed to develop new techniques to gather the widest possible set of high-resolution data and confirm.

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The Mars Express ESA used radar signals bounced through layers
underground ice to identify a water tank buried below the surface.
This image shows an example of radar profile for one of the 29 orbits in the region of
study of 200 x 200 km in the south polar region of Mars. The characteristic bright horizontally
at the top corresponds to the frozen surface of Mars. The layers of deposits
in South pole layers – layers of ice and dust – are at a depth of
about 1.5 km. Below is a base layer in some areas is even
brighter than reflections from the surface, while in other places is rather blurred.
The bright reflections of the base layer, near the center of the image, focus
around 193 ° E / 81 ° S in all orbits intersect describing an anomaly
well defined 20 km wide subsurface which is interpreted as a pool of
liquid water. Credit: ESA / NASA / JPL / ASI / Univ Rome. R. Orosei and other 2018.

This radar, which penetrates beneath the surface, sends pulses to the surface to measure what it takes to bounce back and return to the ship and its intensity. The material properties influence the recovered signal, which makes it possible to map the subsurface topography.

Research shows that the radar region of Mars south pole is formed by several layers of ice and dust with a maximum depth of 1.5 km in area 200 km wide analyzed in this study. Within an area of ​​20 km in diameter it has identified a particularly bright reflection of radar under layers of deposits.

In analyzing the properties of the reflected radar signals and to consider the composition of the layers of deposits and the temperature profile expected under the surface, scientists interpret this bright feature as the connection point between ice and a stable body of liquid water , which may be loaded with saturated saline sediments. For MARSIS has been able to detect it, you should have a minimum thickness of several tens of centimeters.

“This anomaly beneath the surface of Mars has properties that indicate that it is water or water-rich sediments,” says Roberto Orosei, MARSIS experiment’s principal investigator and first author of the article published yesterday in Science. “The study area covers a small area, but it is exciting to think there might be more water pockets elsewhere, yet to be discovered.”

“We’ve spent years seeing signs of underground phenomena of interest but could not reproduce the result of orbit to orbit, since the sampling frequencies and resolution of our data so far were too low” adds Andrea Cicchetti, chief operating officer of MARSIS and coauthor the new article.

“We needed to find a new mode of operation that would avoid some processing on board and allow higher sampling frequency to improve resolution of our data: now we can identify things that we were not able to see before.”

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Trace Gas Orbiter ExoMars captured this view of part of the South Pole ice cap on Mars on May 13, 2018.

ESA/ExoMars Trace Gas Orbiter

The poles of Mars have huge layers of polar ice caps similar to Earth in Greenland and Antarctica ice . These caps are composed primarily of water ice and deposited in layers containing varying amounts of dust. They are known as Mars polar deposits layers (PLD). Thanks to the mass guns dissect layered deposits, orbiting spacecraft in orbit can see the internal layered structure. The imaging system stereo and color Orbiter ExoMars, cassis surface, saw this segment of 7 x 38 km deposits layers frost near the margin of the South PLD, extending as far north as 73 ° S. Here, CASSIS has images of remaining deposits within a crater in this range.

ESA ExoMars Trace Gas Orbiter CASSIS

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CaSSIS flight model. Photo credit: University of Bern

Fine variations in the color and brightness of the layers are visible through the color filters of the camera. It highlights the bright ice deposits redder sand to the top of the image. The ExoMars program is a joint effort between ESA and Roscosmos. Credit: ESA / Roscosmos / cassis, CC BY-SA 3.0 IGO.

The finding points to a certain extent to Lake Vostok, discovered about 4 km under the ice of Antarctica. It is known that certain forms of microbial life thrive in subglacial environments on Earth, but bags of saline groundwater and sediment-rich water of Mars may be a suitable habitat, or have guessed in the past? It is not yet known whether there was life on Mars at some point, a question to which they try to answer Mars missions, including the current Russian-European ExoMars orbiter and rover future.

“The long duration of Mars Express and the huge effort made by the radar equipment to overcome all challenges related to analysis have made this long-awaited result, demonstrating that the mission and its payload still have great scientific potential “says Dmitri Titov, Mars Express project scientist at ESA.

“This fantastic discovery is a milestone for planetology and help us to better understand the evolution of Mars, the history of water on the planet and its habitability.”

Mars Express was launched on 2 June 2003 and 25 December this year will be 15 years in space.

Notes to editors

The article Radar evidence of subglacial liquid water on Mars by R. Orosei et al., Is published in the journal Science.

The MARSIS instrument was funded by the Italian space agency ASI and NASA, and was developed by the University of Rome (Italy) in collaboration with the Jet Propulsion Laboratory (JPL) of NASA.

From European Space Agency

28/8/18
For more information:
Roberto Orosei
MARSIS Principal Investigator
INAF, Bologna, Italy
Email: roberto.orosei@inaf.it

Andrea Cicchetti
MARSIS Operations Manager
INAF, Rome, Italy
Email: andrea.cicchetti@iaps.inaf.it

Dmitri Titov
ESA Mars Express Project Scientist
Email: dmitri.titov@esa.int

Markus Bauer
ESA Science Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int

See the full article here .


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