Mars rover uncovers hints of water activity

The latest close-up inspections of Martian soil and rock by the NASA rovers Spirit and Opportunity continue to provide tantalising and unexpected results. A rock that had looked sedimentary proved to be volcanic, while a freshly-dug trench is showing what may be hints of some recent water activity.

Opportunity has now completed a full set of microscopic imaging and two kinds of spectroscopy inside a trench that it dug earlier this week. By spinning one wheel while locking the other five, the rover gouged out a furrow 50 centimetre long and 10 centimetre deep in the soft, powdery soil.

On Thursday, it placed its instrument arm on six different locations on the side and bottom of the trench. The sides of some tiny spheres were spotted embedded in the soil in the trench side - similar to those seen earlier on the soil and in an outcrop of bedrock.

But the ones in the trench appear shiny and polished. This could indicate sedimentary origins, with the stones becoming buffed gently as they rolled at the bottom of shallow water.

Also, the sand-grain or smaller particles in the soil seem to be clumped or cemented together, says science team member Albert Yen. The clumping suggests salts which can migrate with water vapour through the soil "providing a weak cement," he says.

The team is now looking for evidence of salts in the data just received from the Mossbauer spectrometer and the Alpha-Proton X-ray Spectrometer taken inside the trench.

Opportunity is now heading toward a section of the outcrop, called El Capitan, which seems to include the full suite of layers that is seen in different parts of the outcrop, says team leader Steven Squyres. "There's different kinds of material here" in the bedrock, as revealed by its different rates of weathering, he says.

By going to El Capitan, "from a single rover parking spot, we can reach both parts of the unit" with the robotic arm, according to Squyres.

Meanwhile, on the other side of Mars, the twin rover Spirit has officially reset the record for total distance travelled on Mars. The previous record-holder was the tiny 1997 rover Sojourner which journeyed 102 metres.

Spirit has now gone more than 110 metres from its landing spot and is about halfway to the rim of a crater called Bonneville. The sheer crater rim is expected to provide a window into deeper layers of the soil in this region, which may have once been a lakebed.

There are already some intriguing features being seen there, says David DesMarais, a science team member from NASA's Ames Center. Tiny geometric indentations in the soil there resemble the cracking seen in some soils as they go through periodic freeze-thaw cycles or moistening and drying, either of which could mean the recent presence of some water in the Gusev site's soil, he says.

But one rock that had tantalised the scientists this week turned out to be quite ordinary. Spirit had spotted a rock that looked flaky, resembling the finely-layered rocks seen by Opportunity in its very different location. But closer examination showed this rock to be just ordinary basalt.

I'll just stick this reference in here, even though it is not Mars oriented. Things to come.

http://saturn.jpl.nasa.gov/news/press-releases-01/20010629-pr-a.cfm

. . .

The new plan will change the planned release date and geometry for the part of the mission in which the Huygens probe will parachute into the thick atmosphere of Titan. The new date will be Jan. 14, 2005, seven weeks later than originally planned. The plan will also position the Cassini orbiter farther away during that descent.

. . .

Interesting that they can reprogram their lander bot on the fly. We'll see a lot more of this flexibility in future missions, especially with NASA's new emphasis on robotics (in other words, increased funding.)

Is there plans for a mars driller? How far down will it drill?

Mars Express will look for water using a radar technique.

http://www.planetary.org/mars/mex-inst-marsis.html

MARSIS:

Mars Advanced Radar for Subsurface and Ionospheric Sounding aboard the Mars Express Spacecraft

Scientific Objectives

MARSIS is a radar instrument that is designed to search beneath Mars's surface for liquid water, ice, or permafrost layers. Despite abundant evidence for flowing water on Mars's surface in its past, there is little water on the surface today, so scientists hypothesize that the water either escaped from the atmosphere or sank into the ground. MARSIS will attempt to directly confirm the presence of sub-surface water. Scientists will investigate what form the subsurface water takes and how the depth to the subsurface water varies with local geology, topography, and latitude over the entire planet.

The MARSIS instrument can also be used to measure the scattering properties of the surface of Mars at long wavelengths and to examine the electron density and temperature in Mars's ionosphere.

How It Works

The instrument broadcasts very long wavelength radio waves and observes the time of the reflections, a techique called ground-penetrating radar. Ground-penetrating radar is used on Earth by geologists to prospect for water, oil, rock layers, or rock faults underground.

MARSIS will send low frequency radio waves (1.3-5.5 MHz) towards the planet from a 40 m long antenna which will be unfurled after Mars Express goes into orbit. The radio waves will be reflected from any surface they encounter. For most waves, this will be the surface of Mars. But because of the low frequency, a significant part of the waves will travel through the crust to depths of 2 to 5 kilometers to encounter further boundaries between layers of different material. For boundaries between materials of different types--like ice and rock, or sand dunes and bedrock--there should be a detectable radar echo. It may even be possible for MARSIS to detect boundaries between different lava flows.

The time delay between the surface reflection and any subsurface reflections will allow scientists to determine the depth to the boundary. The time differences involved are tiny, measured in nanoseconds (billionths of a second). This experiment has only been made possible by the development of a new, highly precise, very compact clock for the spacecraft to measure these tiny time increments.

MARSIS will work best at night when the Martian ionosphere is least active and when the spacecraft is less than 800 km from the Martian surface, a condition that occurs for 26 minutes during each 6.75 hour orbit.

How Does MARSIS Fit In the Context of Planetary Exploration?

The MARSIS subsurface sounding instrument is the first of its kind ever flown on any mission. The technique was successfully tested on the Moon during one of the Apollo missions, and ground-penetrating radar has been used for decades on Earth to study the subsurface.

I'm a bit familiar with this stuff from way back when communication procedures - long and slow waves move through earth and rocks....
OK, so how does this fit:
"The time delay between the surface reflection and any subsurface reflections will allow scientists to determine the depth to the boundary. The time differences involved are tiny,...made possible by the development of a new, highly precise, very compact clock for the spacecraft to measure these tiny time increments. (and)...will work best at night when the Martian ionosphere is least active...a condition that occurs for 26 minutes during each 6.75 hour orbit."???

It's moving fast enough to orbit in 6.75 hours, the window is 1/14th of that time, the waves are long and slow and have to rebound to the orbiter:
Seems to me that this is gonna yield about two 'pictures' a day and that it's going to be limited to a small patch of Mars.

Is that enough to draw conclusions from?

PS: exception to use of 'clock' in this instance - chronometer would be more approptiate.
and,
from my limited understanding, "tiny time increments" is a misnomer as well.

Here's yet another space launch coming up quickly; maybe it needs its own thread, but it isn't NASA:

http://spaceflightnow.com/ariane/v158/status.html

Follow the preparations and launch of the Arianespace Ariane 5 rocket carrying the European Space Agency's Rosetta comet explorer. Reload this page for the very latest on the mission.

WEDNESDAY, FEBRUARY 25, 2004

Europe's vaunted $1 billion Rosetta comet explorer is poised to set off on its decade-long journey early Thursday morning from the same South American launch site that hosted the start of the continent's first deep space mission 19 years ago.

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