# Presentation: 484537

## Week in Review               February 29 - March 5

**Week in Review               February 29 - March 5**

**Spirit               and Opportunity **

**Mars Exploration Rover Mission**

## Spirit began the week by brushing dust from three spots on a

**Spirit began the week by brushing dust from three spots on a**
**rock called “Humphrey,” giving Mars scientists a larger, cleaned area to study.**

**Spirit, 2/29/04**

## A few days later, Spirit had used the Rock Abrasion Tool for four hours to drill a 

**2-millimeter-deep (.08-inch) hole into Humphrey so that the science team could study its interior.**

**Spirit, 03/03/04**

**Notes:**
sol 59, Mar 03, 2004: Rock Abrasion Tool Back in Action

Waking up to "One More Time" by The Real McCoy, Spirit completed a successful, 2 millimeter-deep grind (.08 inches) into a target slightly left of the depression it made yestersol during its abbreviated operation. A five-minute brush to clean the hole followed.

Completing the sol, which ended at 8:31 p.m. Wednesday, March 03, Spirit's arm then switched instruments so the Moessbauer spectrometer could examine "Humphrey's" new shallow cavity.

Before this sol's four-hour grinding, the microscopic imager and the alpha particle X-ray spectrometer finished observations of yestersol's rock abrasion tool depression. To document Spirit's current position - about halfway to the "Bonneville" crater rim - the panoramic camera snapped the first of several images that, together, will provide a 360-degree view.

Engineers identified the software issue that caused the rock abrasion tool to terminate its original planned grinding on sol 58. The minor bug will be fixed when new flight software is loaded at the end of March.

In the coming sols, Spirit will complete the alpha particle X-ray spectrometer observations of the rock abrasion tool hole and get an up-close view with the microscopic imager. The final images will be obtained for the full panoramic view of Spirit's current position. After miniature thermal emission spectrometer and panoramic camera observations of the hole are conducted, Spirit will continue on toward "Bonneville" crater.

## Spirit used the microscopic imager to reveal interesting features on Humphrey’s newly exposed surface that give clues to Mars’ geologic history.

**Spirit, 03/03/04**

## Could bright material in the interior crevices of Humphrey be minerals that crystallized 

**Could bright material in the interior crevices of Humphrey be minerals that crystallized **
**out of water?**** **** **
**Small amounts of water with minerals may have been in the original magma that formed this volcanic rock.  Only more tests will tell for sure.**

**Spirit, 03/05/04**

**Notes:**
Volcanic Rock in Mars' Gusev Crater Hints at Past Water
March 5, 2004

NASA's Spirit has found hints of a water history in a rock at Mars' Gusev Crater, but it is a very different type of rock than those in which NASA's Opportunity found clues to a wet past on the opposite side of the planet.

A dark volcanic rock dubbed "Humphrey," about 60 centimeters (2 feet) tall, shows bright material in interior crevices and cracks that looks like minerals crystallized out of water, Dr. Ray Arvidson of Washington University, St. Louis, reported at a NASA news briefing today at NASA's Jet Propulsion Laboratory, Pasadena, Calif. He is the deputy principal investigator for the rovers' science instruments.

"If we found this rock on Earth, we would say it is a volcanic rock that had a little fluid moving through it," Arvidson said. If this interpretation is correct, the fluid -- water with minerals dissolved in it -- may have been carried in the original magma that formed the rock or may have interacted with the rock later, he said.

The clues appear in an interior exposure of "Humphrey" where Spirit's rock abrasion tool scraped away the rock's surface to a depth of 2 millimeters (.08 inch). To gain more confidence that the bright material seen in cracks and pores is not dust that has intruded from the surface over the millenia, scientists intend to have Spirit grind more deeply into another dark rock, not yet selected. The bright material is not debris from the grinding process, said Stephen Gorevan of Honeybee Robotics, New York, lead scientist for the abrasion tool.

The amount of water suggested by the possible crystals in "Humphrey" is far less than what is indicated by the minerals and structures that Opportunity has revealed in rocks at Meridiani. Rover scientists announced the Opportunity findings earlier this week. "Mars is a diverse planet," Arvidson said today.

Spirit is headed toward a crater nicknamed "Bonneville," about 150 meters (500 feet) in diameter, where scientists hope to see rocks from beneath the region's surface volcanic layer. Those rocks may tell yet a different story from an earlier era of Gusev Crater's past. 

## Meanwhile, on the other side of the red planet, Opportunity was conducting studies at the crater rock outcrop, on the verge of the biggest Mars Exploration Rover discovery yet....

**Opportunity**

**Meanwhile, on the other side of the red planet, Opportunity was conducting studies at the crater rock outcrop, on the verge of the biggest Mars Exploration Rover discovery yet....**

**Notes:**
A Treasure Trove of Martian Rocks

This high-resolution image captured by the Mars Exploration Rover Opportunity's panoramic camera highlights the puzzling rock outcrop near the rover's landing site. Opportunity has been investigating the outcrop with the suite of scientific instruments located on its robotic arm. These layered rocks measure only 10 centimeters (4 inches) tall, about the height of a street curb. Data from the panoramic camera's near-infrared, blue and green filters were combined to create this approximate, true-color image. This same image was previously released on Jan. 28, 2004 (PIA05163). 

## Discovery would come at the site named 

**Discovery would come at the site named **
**“****El Capitan,” where 4 details point to a water-soaked past **
**on Mars.**

**Opportunity**
**03/02/04**

**Notes:**
The Texture of El Capitan

This image, taken by the panoramic camera on the Mars Exploration Rover Opportunity, shows a close up of the rock dubbed "El Capitan," located in the rock outcrop at Meridiani Planum, Mars. This image shows fine, parallel lamination in the upper area of the rock, which also contains scattered sphere-shaped objects ranging from 1 to 2 millimeters (.04 to .08 inches) in size. There are also more abundant, scattered vugs, or small cavities, that are shaped like discs. These are about 1 centimeter (0.4 inches) long.

## Water Sign #1:

**Water Sign #1:**
**SPHERULES**
**This close-up, microscopic  image of El Capitan reveals one of many “BB-sized” spherules found in the rock outcrop.  They may be accretions of minerals that formed in porous, water-soaked rocks. **

**Opportunity**
**03/02/04**

**Notes:**
 This image, taken by the microscopic imager on the Mars Exploration Rover Opportunity, shows a geological region of the rock outcrop at Meridiani Planum, Mars dubbed "El Capitan." Light from the top is illuminating the region. Several images, each showing a different part of this region in good focus, were merged to produce this view. The area in this image, taken on Sol 28 of the Opportunity mission, is 1.3 centimeters (half an inch) across.

 Round particles the size of BBs are embedded in the El Capitan outcrop. From shape alone, these spherules might be formed from volcanic eruptions, from lofting of molten droplets by a meteor impact, or from accumulation of minerals coming out of solution inside a porous, water-soaked rock. Opportunity's observations that the spherules are not concentrated at particular layers in the outcrop weigh against a volcanic or impact origin, but do not completely rule out those origins. 

## Water Sign #2:

**Water Sign #2:**
**“****VUGS”**
**On earth, this texture occurs when crystals of salt minerals form within rocks sitting in briny water.  At El Capitan, small cavities called “VUGS” may be voids left when the crystals disappeared.  Water may have dissolved them**
**over time.**

**Opportunity**
**03/02/04**

**Notes:**
Vugs Provide Clues to Martian Past

This image, taken by the microscopic imager on the Mars Exploration Rover Opportunity, illustrates the shapes of the vugs, or small cavities, located on the region dubbed "El Capitan." The region is part of the rock outcrop at Meridiani Planum, Mars, which the rover is currently examining.

The image provides insight into the nature of the rock matrix -- the rock material surrounding the vugs. Several vugs have disk-like shapes with wide midpoints and tapered ends. This feature is consistent with sulfate minerals that crystallize within a rock matrix, either pushing the matrix grains aside or replacing them. These crystals are then either dissolved in water or eroded by wind activity to produce vugs.

The rock matrix here exhibits a granular texture, delicately enhanced through wind abrasion. The primary sediment particles making up this granular layer are relatively uniform in size, ranging up to 1 millimeter (.04 inches). Note that some of these grains are well rounded, which could result from transport of rock fragments in air or water, or precipitation of mineral grains in water. 

## Water Sign #3:

**Water Sign #3:**
**CROSSBEDDING**
**Angled, layered **
**patterns **
** ****(crossbedding)**
** ****give clues to the **
**rock’s formation. **
**The rock called “Last Chance” has concave, small-scale, rippled layers that may **
**have formed in**
**moving water.**

**Opportunity**
**03/02/04**

**Notes:**
Ripples in Rocks Point to Water

This image taken by the Mars Exploration Rover Opportunity's panoramic camera shows the rock nicknamed "Last Chance," which lies within the outcrop near the rover's landing site at Meridiani Planum, Mars. The image provides evidence for a geologic feature known as ripple cross-stratification. At the base of the rock, layers can be seen dipping downward to the right. The bedding that contains these dipping layers is only one to two centimeters (.4 to .8 inches) thick. In the upper right corner of the rock, layers also dip to the right, but exhibit a weak "concave-up" geometry. These two features -- the thin, cross-stratified bedding combined with the possible concave geometry -- suggest small ripples with sinuous crest lines. Although wind can produce ripples, they rarely have sinuous crest lines and never form steep, dipping layers at this small scale. The most probable explanation for these ripples is that they were formed in the presence of moving water.  
Layers in the rock that lie at an angle to the main layers, a pattern called crossbedding, can result from the action of wind or water. Preliminary views by Opportunity hint the crossbedding bears hallmarks of water action, such as the small scale of the crossbedding and possible concave patterns formed by sinuous crestlines of underwater ridges. 

## Water Sign #4:

**Water Sign #4:**
**MINERAL **
**ANALYSIS**

**Spirit detected the presence of an iron-bearing mineral called jarosite. On Earth, jarosite forms in dilute sulfuric acid in ground water.   **

**Opportunity**
**03/02/04**

**Notes:**
Mineral Tells Tale of Watery Past

This spectrum, taken by the Mars Exploration Rover Opportunity's Moessbauer spectrometer, shows the presence of an iron-bearing mineral called jarosite in the collection of rocks dubbed "El Capitan." "El Capitan" is located within the rock outcrop that lines the inner edge of the small crater where Opportunity landed. The pair of yellow peaks specifically indicates a jarosite phase, which contains water in the form of hydroxyl as a part of its structure. These data suggest water-driven processes exist on Mars. Three other phases are also identified in this spectrum: a magnetic phase (blue), attributed to an iron-oxide mineral; a silicate phase (green), indicative of minerals containing double-ionized iron (Fe 2+); and a third phase (red) of minerals with triple-ionized iron (Fe 3+). 

## Opportunity will traverse toward “Slick Rock” in the “Berry Bowl” area, where many spherules have collected.

**Opportunity will traverse toward “Slick Rock” in the “Berry Bowl” area, where many spherules have collected.**

**Spirit will continue its 25-meter (82-foot), northeast journey toward the heavily rock-strewn edge of Bonneville crater.  **

**COMING UP!**

**Notes:**
sol 40, Mar 05, 2004: Opportunity Fit At Forty

After 40 good days on the surface, Opportunity is showing no signs of middle age.

On sol 40, which ended at 9:32 a.m. PST, March 5, 2004, Opportunity finished a set of overnight alpha particle X-ray spectrometer measurements at "Last Chance" and completed a morning set of panoramic camera and miniature thermal emission spectrometer remote sensing observations. At 11:30 Local Solar Time, engineers retracted the alpha particle X-ray spectrometer off the target, took a final set of 24 microscopic images, and stowed the arm for driving.

Opportunity then scored another first by successfully using visual odometry to navigate autonomously on Mars. During a drive along the crater wall, the vehicle properly identified wheel slippage on the steep slope of the crater wall using features in the navigation camera imagery. This effectively provided a mid-course correction that landed the science and engineering team exactly at the target location where they want Opportunity to do work using the instruments on the rover arm on sol 41.

The plan for sol 41, which will end at 10:12 a.m. PST, March 6 will be to take microscopic images of an area dubbed "Wave Ripple" in the "Last Chance" area, followed by a traverse to "Slick Rock" in the "Berry Bowl" area.