Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Evidence for rain on Mars?

25.09.2008
Evidence that lake deposits once formed inside impact craters on Mars has been presented today at the European Planetary Science Congress in Münster.

About four billion years ago, there were lakes on Mars which may have been fed by short-lived rivers that were, in turn, fed by precipitation. These lakes filled craters that were formed by the impact of meteorites. Water accumulated in places where rivers broke through the crater rims.

Deltas were formed at the mouths of the rivers, similar to how they are formed where rivers flow into lakes or seas on Earth. These are the findings of an international team of researchers led by Ernst Hauber of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), who analysed the latest image data of the Martian surface. They discovered delta deposits in these images, relatively unaffected by erosion, inside the craters.

The scientists explored the Xanthe Terra area located near the equator in the Martian highlands. "For years scientists have been suspecting that the current appearance of the landscape has, in part, been shaped by rivers that cut into the surface," explains Mr Hauber. The geologist of the DLR Institute of Planetary Research (DLR-Institut für Planetenforschung) in Berlin-Adlershof led the research efforts and their results will be published in the scientific journal Planetary and Space Science. “We can see layered sediments where these valleys open into impact craters. The shape of certain sediments is typical for deltas formed in standing water."

The researchers analysed images from three Mars spacecrafts. These images were recorded by the German HRSC stereo camera on board the European Mars Express mission, by the Mars Orbiter Camera (MOC) on board NASA's Mars Global Surveyor Mission and by the HiRISE and CTX camera experiments on board NASA's Mars Reconnaissance Orbiter (MRO) mission. The HRSC, which is operated by DLR, enables the high-resolution and "3-D" representation of large contiguous areas. So-called digital terrain models can be derived from these representations and the topography of the Martian landscape can be calculated. The data recorded by the HiRISE camera on board the MRO make it possible to explore small, specifically selected areas in images which show details on Mars that are not much more than a metre in size.

Rivers carry eroded material downstream. When the flow rate drops, there is not enough energy left to transport this sediment load and it will be deposited. Because this typically happens in places where a river flows into a larger basin, and where the flow rate nearly completely drops to zero, sedimentary deposits form in such locations. The type of deposit then depends on the nature of the basin. If the basin is filled with water - a lake or a sea - deltas are formed. If on the other hand the basin is dry, for instance in the desert, the river slows down and gradually seeps away, in some cases forming so-called playas in the process. Deposits in such dry areas are called alluvial fans. Analysis of sedimentary bodies can therefore show if there were lakes on Mars.

The Xanthe Terra highlands in the equatorial region of Mars are traversed by deeply incised valleys. Scientists have suspected for a long time that these were formed by water erosion. A particularly beautiful delta can be found here in a small crater with a diameter of only five kilometres. The Nanedi river opens into the crater from the south (in the lower part of the image), where the sedimentary material is distributed over a fan-shaped area. The crater is almost completely filled with sediments. Topographic data derived from the stereo images recorded by the HRSC camera show that the layer of material is at least 50 metres thick and the deposits cover an area of about 23 square kilometres.

Very thin layers can be seen along the edge of the deposits. Such thin layers are also typical for deltas on Earth. A particularly interesting discovery is the small valley which leaves the crater towards the east (towards the right in the image). This provides evidence that water must have indeed been "standing" in the crater. "If the water flowed into the crater and back out again, it must have filled it up as well", says Mr Hauber. He points out that it is quite rare to see something like this on Mars: "In this and in a few other cases, we are fairly certain that there were lakes on Mars".

The researchers can also narrow down the period when the craters were filled with lakes. In order to do so, they analyse the statistical distribution of impact craters of different sizes. These give an indication of the age of a planetary surface. The more craters are counted on a surface, the older the area is. The crater counts revealed that water was flowing through the valleys between about 4 and 3.8 billion years ago. The valleys themselves could have formed relatively fast. Maarten Kleinhans of the University of Utrecht in the Netherlands, who also participated in the research study, calculated that depending on the water volume, the deposits could have formed over a period ranging from decades to millennia. According to Mr Kleinhans, even if the water flow was very low, it would not have taken more than a few hundred thousand years for the deltas to reach their current dimensions. Compared to other geological timescales, especially in planetary geology, this is a very short period of time.

Thus, there must have been precipitation on early Mars. This precipitation then flowed over the surface – this is also one of the findings of the joint research effort. "This is actually not at all self-evident: for a long time, scientists have been trying to figure out whether the valleys on Mars were formed by groundwater seepage and headward erosion, or by surface runoff caused by rainfall or snowmelt", says Mr Hauber. In recent discussions, the role played by surface runoff has been emphasised again. "Our findings also point in this direction and we are convinced that both processes have played an important role in Xanthe Terra".

However, this situation did not last very long. Between 3.8 and 3.5 billion years ago, the precipitation became less intense and the valleys dried up. Erosion on Mars has been minimal ever since, which has contributed to the fact that deposits can still be observed although they should in fact be very susceptible to erosion. Today, Mars is a dry desert planet and water is no longer flowing through its valleys.

Anita Heward | alfa
Further information:
http://www.europlanet-eu.org

More articles from Physics and Astronomy:

nachricht New survey hints at exotic origin for the Cold Spot
26.04.2017 | Royal Astronomical Society

nachricht NASA's Fermi catches gamma-ray flashes from tropical storms
25.04.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Link Discovered between Immune System, Brain Structure and Memory

26.04.2017 | Life Sciences

New survey hints at exotic origin for the Cold Spot

26.04.2017 | Physics and Astronomy

NASA examines newly formed Tropical Depression 3W in 3-D

26.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>