Update 3/4/2004: Nature Science Update has the best description of the science.
Update: The AP story of this is found here.
I will blog this live as I am watch the NASA channel on the press conference for the Mars Rover.
Ed Weiler: 3 1/2 years a number were on the stage telling to send two rovers to look for water activity. They gave their dreams to find their dreams for water. Opportunity was on an area where liquid water was drenched in the past. They are laying down the new vision of exploration as defined by the President.
Steve Squyres: They have been puzzling out the outcrop on the Mariani Plain. The German instruments have helped puzzling them out. The last puzzle piece. The rocks were once "soaked in liquid water". Were the layered rocks layed down by liquid water. They have some tantalizing clues in two weeks or so. Were the rocks altered by liquid. A definitive yes. Four pieces of evidence:
1. Little spherical objects a few mm in size. Named "blueberries" because they were embedded like in a muffin. Were they lapilli -- volcanic hail stone? Were they droplets of volcanic glass? They have looked at the objects in many ways. All the clues led them to be concretions. Liquid water in rock they precipitates out from a nucleation agent that grows into a spherical object.
2. Shot through with tabular holes (long and thin). Shot through the rock. Like rocks on earth when crystals grow in rocks. If the crystals are tabular. Water dissolves or erode away the tabular holes.
3. Alpha particle X-Ray spectrometer. Much sulphur. Outside of rock had a coating? RAT ground the rock and looked at it again. Even more sulpher. Too much to explain other than sulphate salts. Telltale sign of liquid water. Mni-TAS found evidence of sulphate salts
4. Jarocite Fairly rare. Predicted as might be found on Mars someday. Sulphate/hydrate, must have water.
Put the story together. Hard to avoid the conclusion of liquid water. Purpose of the mission to find habitable environment. At some point in time this was habitable for life. Don't know if it was there, but it could have. Best kinds of rock for ancient earth life these kinds of rocks are helpful. They can trap the evidence. Very good targets for continued investigation.
We have tenative evidence. Modified by liquid water but may have been laid down by water. Big Bend will have very detailed images to determine if laid down by liquid water.
Show movie of outcrop. Layering is ubiquitous. El Capitan reminded of Guadalupe Mtns of Texas. Still see layers. More lamination and voids and blueberries. Lamination comes up to spherules are concretions of sedimate. Spherules are randomly distributed. Tabular taper at the ends like earth mineral gypsum. Could have been eroded by wind, also, though. Seven days of experiment to look at "last chance". Details of cross-bedding. Layers are inclinded to the principal bearing planes. Requires sediment to move in a flowing current. Could be other liquids.
Looking at the spectrometer data: APXS shows sulpher is much higher in outcrop also Bromine also differential to original landing sight. Knew sulpher was high at Viking mission. Could have been salts. Chlorine was constant but Sulphate change near layered outcrop. This is an evaporitic sequence. The salts precipitate out. Four different kinds of minerals. Jarocite is a very high concentration of the iron. Many lines of chemical evidence of a strong indication of very salt in the outcrop.
Next question. How extensive was the liquid water? Go to crater Endurance. Crater has bright rim. Interested if the bright rim is the same as the outcrop rock. Maybe a different water story. Look at older rocks in the crater. Finding out if the bright material of the mottled terrain is the same kind of stuff.
New mission. MRO. Looking for the same stuff from orbit. These rocks for ancient habitats on Mars. Want to bring rocks home. One example we really want to bring it home. Look at the President's vision to design a mission to bring this back. We know a good place to find rocks for the labs. Roving vehicle to collect and drive them up to mother ship to return to earth labs to find microfine details. First step to see the new Mars.
Cannot yet tell the waters are laid down in a pool. Don't know about depth yet. The best way to get at age of water is bring it back. Want to see how thick the layering. Can't talk about age or duration without some more moving around.
President's initiative will include a sample return, astrobiology missions, prep for human landings (e.g. toxicity). Some mission totally science oriented, human prep, probably a combination of the two. Predictions of the future may be dangerous, though.
Don't know timeframe of habitability, yet. Still some interesting things may happen at Spirit site. Gusev out of the plain. When Spirit gets to a crater than maybe find out some other information. A lot more work to do before answer on habitability.
Finding fossils on ancient rocks is very rare. First look for place for preservation. These are ideal time capsules to find such fossils if they are there. Nevertheless, a bit of a challenge.
Sulpher gets fractionated differently by life than by other mechanisms. Could do a chemical test to look for such clues and do an isotopic analysis. MSL may have isotopic tools but a challenge to get in by '09.
Evidence of soaking: Massive quantities of sulphate.
Not a well-defined basin so hard to imagine this as a pool.
Another week to ten days in this crater and go to Big Bend to look for cross beds and ripples. One thing we don't know what spherules are made of. There is bowl space called the blueberry bowl and look at composition of them. Another few days. Then crawl out of the crater and look for a few sols and go towards endurance crater. Opportunity will catch up on travel with respect to Spirit. 50 to 100 meters per day, maybe. Hematite was a chemical beacon to something interesting chemically. More hematite outside of the crater.
One possibility water percolates from below. Other scenario: a salty sea, water currents, and waves. Look at possibility water sloshing. Water evaporates away. Both are possible given current evidence. Big Bend may show which may be more likely.
Habitable means suitable for life given organisms we know from Earth.
This was from a different from long ago. A different Mars than from what we see today.
Go to Big Bend and Last Chance suggest some cross-bedding. The geometries will tell us if it flow of current is involved. Hope to constrain the mechanisms involved.
Cross-bedding may not be real. Need to get closer and look at the specific geometries for answers on current flow.
Need to get Bonneville Crater to possibly find similar stuff at Spirit site. Need a wider range of materials. Need to ask these question in a few weeks with respect to water at the Spirit site.
Phoenix mission will explore ice regions.
Final quote from Steve Squyres: We all went into this landing site with all our prejudices. As we acculate the evidence piece by piece, it was interestingly each of us to come to the conclusion. Some lept over the cliff and others dragged. On one hand it was very gratifying. On the other hand, we are just started. We are enjoying at looking at every cm of the outcrop. But also want to get out of it.