Curiosity Finds Evidence of An Ancient Streambed on Mars
The Curiosity rover has come across a place in Gale Crater where ankle-to-hip-deep water once vigorously flowed: an ancient stream-bed that may turn up paydirt!
This area contains evidence of gravel that has been worn by water. At a press briefing today, members of the Mars Science Laboratory team said the rover has found “surprising” outcrops and gravel near the rover landing site that indicate water once flowed in this region, and likely flowed for a long time.
“Too many things that point away from a single burst event,” said Curiosity science co-investigator William Dietrich of the University of California, Berkeley. “I’m comfortable to argue that it is beyond the 1,000 year timescales, even though this is very early on in our findings.”
From the size of gravel found by the rover, the science team can interpret the water was moving about 1 meter (3 feet) per second, with a depth somewhere between ankle and hip deep.
“Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them,” said Dietrich. “This is the first time we’re actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it.”
What Curiosity found on Mars was described as conglomerate rock made up of water-transported gravels, meaning the gravel is now cemented into a layers of rock, and the sizes and shapes of stones offer clues to the speed and distance of a long-ago stream’s flow.
“The shapes tell you they were transported and the sizes tell you they couldn’t be transported by wind. They were transported by water flow,” said Curiosity science co-investigator Rebecca Williams of the Planetary Science Institute.
The discovery comes from examining two outcrops, called “Hottah” and “Link,” with the telephoto capability of Curiosity’s mast camera during the first 40 days after landing. Those observations followed up on earlier hints from another outcrop, named Goulburn, which was exposed by thruster exhaust as Curiosity touched down.
“Hottah looks like someone jack-hammered up a slab of city sidewalk, but it’s really a tilted block of an ancient streambed,” said Mars Science Laboratory Project Scientist John Grotzinger of the California Institute of Technology.
Even though the team classified the finding as “surprising,” they later said they actually weren’t too surprised at what they found so early in the mission – just 51 sols, or Martian days, in.
“We are getting better about integrating the orbital data,” said Grotzinger. “We see an alluvial fan and debris flow from orbit, and then see these water-transported pebbles from the ground. This is not rocket science, but shows exactly the reason we chose this landing site, and you build on those foundations you think you are mostly likely to establish. Now we’ll look at more rocks and get more context to recreate the environment in greater detail along with understanding the chemistry of the time to see if this is a place that could be habitable.”
Asked if it was hard to come to consensus on this long-term, quickly flowing water statement, given the large number of scientists involved with the mission, Grotziner said, “Given the evidence we have from orbit that has been analyzed, when we arrive with a robot we can test the hypothesis pretty quickly. If the geological signal for this process is large enough, it is easy to achieve a consensus pretty quickly.”
The finding site lies between the north rim of Gale Crater and the base of Aeolis Mons, or Mount Sharp, a mountain inside the crater. To the north of the crater, a channel named Peace Vallis feeds into the alluvial fan. The abundance of channels in the fan between the rim and conglomerate suggests flows continued or repeated over a long time, not just once or for a few years, the science team said.
But interestingly, the rover has already moved on from this spot, and yesterday took the longest drive yet, of between 52-53 meters, heading towards the Glenelg region where they want to do their first scooping and tests soil samples in Curiosity’s two instruments, SAM (Sample Analysis at Mars) and ChemMin (Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument). These two experiments will study powdered rock and soil samples scooped up by the robotic arm.
The Glenelg area marks the intersection of three kinds of terrain: bedrock for drilling, several small craters that may represent an older or harder surface, and also terrain similar to where Curiosity landed, so the science team can do comparisons.
“A long-flowing stream can be a habitable environment,” said Grotzinger. “But it is not our top choice as there might be other places that have preserved organic carbon better than this, and we need to assess the potential for preservation of organics. We’re still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment.”
The slope of Aeolis Mons contains clay and sulfate minerals, which have been detected from orbit. This can be good preservers of carbon-based organic chemicals that are potential ingredients for life.
As for what’s next for Curiosity, Grotzinger said they have a couple of targets in the next 2-4 sols, and then they will park for a long period of time, about 2-3 weeks to prepare for reaching Glenelg. “This is such a complex set of processes that have never been done on Mars before, so we are going to be conservative and go slowly to make sure everything is working as it should. Then we’ll go to Glenelg and choose first candidate for drilling.” Source: Universe Today
GALE CRATER SET FOR SUMMER HEAT WAVE?
Preliminary weather reports from the Curiosity’s Remote Environment Monitoring Station (REMS) are showing some surprisingly mild temperatures during the day. Average daytime air temperatures have reached a peak of 6 degrees Celsius at 2 pm local time. A Martian day — known as a sol — is slightly longer than Earth’s at 24 hours 39 minutes. Temperatures have risen above freezing during the day for more than half of the Martian sols since REMS started recording data. Because Mars’s atmosphere is much thinner than Earth’s and its surface much drier, the effects of solar heating are much more pronounced. At night the air temperatures sink drastically, reaching a minimum of -70 degrees just before dawn.
NASA’s Mars Science Laboratory touched down in Gale Crater on 5th August 2012 close to the equator of Mars at a latitude of 4.5 degrees south. The southern hemisphere of Mars is approaching springtime, leading to speculation about possible temperatures at the height of Martian summer.
“That we are seeing temperatures this warm already during the day is a surprise and very interesting,” says Dr. Felipe Gómez of the Centro de Astrobiología in Madrid. “It’s very early days and we are only now being able to test our models against REMS observations. If this warm trend carries on into summer, we might even be able to foresee temperatures in the 20s — and that would be really exciting from a habitability point of view. In the daytimes, we could see temperatures high enough for liquid water on a regular basis. But it’s too soon to tell whether that will happen or whether these warm temperatures are just a blip.”
REMS pressure sensors have also been recording slightly higher pressures than expected. In winter, Mars becomes cold enough for carbon dioxide at the poles to freeze, forming seasonal ice caps. Since carbon dioxide makes up most of the atmosphere, this process causes the overall atmospheric pressure to vary through the year. Models and data from previous mission predicted that Curiosity would land around the minimum mean pressure for the year. So far, the pressure measurements from REMS do indeed appear to be rising slowly. The pressure has risen from a daily average of around 730 pascals during the first three weeks after landing to around 750 pascals — a tiny fraction of the average pressure at sea level on Earth.
“The pressure data show a very significant daily variation of pressure, following a fairly consistent cycle from sol-to-sol. The minimum is near 685 pascals and the maximum near 780 pascals. The majority of the variation is due to large scale waves in the atmosphere called tides. These tides are different from tides in the Earth’s ocean because they are forced by heating due to the Sun rather than the gravitational pull of the Moon. The tides are sensitive to the distribution of cloud and dust in the atmosphere, and also the large scale pattern of winds — rather like the jet streams on Earth,” says Javier Gómez-Elvira, the Principal Investigator of the REMS Instrument. Source: The Europlanet Research Infrastructure