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Science Investigations

Water is a key to at least four of the most critical questions about Mars: Has Mars had

life? Could Mars support human outposts? Can Mars teach us helpful information

about climate change? Do Mars and Earth share the same geological processes? 

Water is a prerequisite for life, a potential resource for human explorers and a major

agent of climate and geology. That's why NASA has pursued a strategy of "follow the

water" with spacecraft sent to Mars in recent years, resulting in discoveries such as

fresh gullies carved by fluid, copious ice mixed into the top layer of surface material

and ancient rock layers formed under flowing water. 

The Mars Reconnaissance Orbiter mission will follow the water further. The string of

water-related discoveries by spacecraft currently at Mars leave many questions that

this orbiter is well equipped to investigate. We now know there was standing water on

the planet. How extensively? How long? How often? Where did it well up from under-

ground and where did it flow down from uphill drainage networks? 

Deciphering the relationships among today's layers of material at and near the surface

will help scientists answer these questions and raise new ones. For example, Mars

Reconnaissance Orbiter may be able to resolve whether layers seen in the walls of

canyons such as Valles Marineris are pasted on from the slumping of walls above

them, as they might be if water emerged from the walls, or exposures of underlying

layers emplaced before the deepening of the canyon cut through them, like in

Arizona's Grand Canyon. How large an area and how long a period is evidenced in the

water-related layers around Opportunity's landing site in Meridiani Planum?

Observations by Mars Reconnaissance Orbiter may improve estimates of the answers

by tracing the edges of layers and following where one extends beneath another.

Mars has shown surprises each time researchers have used increased resolution to

examine it. The surface bears diversity in mineral composition and physical structure

down to the smallest scales discernable from orbit so far. Researchers anticipate that

the considerably higher resolution and coverage possible with Mars Reconnaissance

Orbiter will reveal more. For example, the mission might find deposits of water-related

minerals that don't cover enough ground to be detected by previous orbiters. 

Science Objectives

Since its early planning stages, the Mars Reconnaissance Orbiter mission has had

three underlying science objectives: 

1. Advance our understanding of Mars' current climate, the processes that have

formed and modified the surface of the planet, and the extent to which water

has played a role in surface processes.

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2. Identify sites where possible effects of liquid water indicate environments that 

may have been conducive to biological activity or might even now harbor life. 

3. Identify and characterize sites for future Mars landings.

In pursuit of these objectives, the mission will make observations and measurements

to:

Assess Mars' seasonal and time-of-day variations in water, dust and carbon 

dioxide in the atmosphere. 

Characterize Mars' global atmospheric structure and surface changes.

Search for sites with evidence of water or hydrothermal activity.

Examine the detailed stratigraphy (layers laid down over time), geologic 

structure and composition of Mars' surface features.

Probe beneath the surface for evidence of subsurface layering, reservoirs of 

water or ice, and the internal structure of polar ice caps.

Map and monitor the Martian gravity field to improve knowledge about Mars' 

crust and variations in atmospheric mass.

Identify and characterize prospective landing sites with high potential for 

discoveries by future missions.

Research Strategy

The orbiter will use a wide range of wavelengths for its investigations, from ultraviolet

through visible and infrared to short-wave radio. It will see Mars' surface in greater

detail than any previous Mars orbiter. 

The tremendous amount of data generated by observations in many wavelengths and

at high resolutions dictates the importance of the orbiter's large high-gain antenna and

high-powered telecommunications system for sending the data to Earth. Nevertheless,

limits on time and data capacity mean that only a small fraction of Mars can be exam-

ined at the highest resolution. The surface of Mars covers an area about the same as

all the dry land on Earth. Surprises detectable with this orbiter's capable instruments

could lie anywhere. Choosing where to look closely will affect what discoveries are

made.

To make the most effective use of the highest-resolution capabilities, the mission's sci-

ence team will employ a strategy of mixing three distinct modes of observations: daily

global-scale monitoring, regional surveys and targeted high-resolution observations.

The broader views will aid interpretation of the higher-resolution data and will identify

additional sites for targeted observations. Some instruments can observe in more than

one mode. Targeted observations may combine nearly simultaneous data collection by

more than one instrument, providing context for interpreting each other's data.

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Science Instruments

Mars Reconnaissance Orbiter will carry six science instruments. Two additional investi-

gations will use the spacecraft itself as an instrument.

The High Resolution Imaging Science Experiment will photograph selected

places on Mars with the most powerful telescopic camera ever built for use at a foreign

planet. It will reveal features as small as a kitchen table in images covering swaths of

Mars' surface 6 kilometers (3.7 miles) wide. Combining images taken through filters

admitting three different portions of the spectrum will produce color images in the cen-

tral portion of the field of view. Paired images of top-priority target areas taken from

slightly different angles during different orbits will yield three-dimensional views reveal-

ing differences in height as small as 25 centimeters (10 inches). 

Of the orbiter's three research modes (global monitoring, regional survey and targeted

observations), this instrument's role will be in the targeted-observation mode.

Researchers will use the high-resolution camera to examine shapes of deposits and

other landforms produced by geologic and climatic processes. As one example, they

will look for boulders in what appear to be flood channels, which would be evidence

that the channels were cut by great flows of water, rather than glaciers or lava flows.

And they will check the scale of layering in polar deposits. Those layers are believed to

result from cyclical variations in Mars' climate; their thickness could be an indication of

the time scale of climate cycles. Some layers are at least as thin as the current limit of

resolution in orbital images, so higher-resolution imaging will add more information for

deciphering climate history. Other anticipated targets include gullies, dunes and pat-

terned ground.

This camera has a primary mirror diameter of 50 centimeters (20 inches) and a field of

view of 1.15 degrees. At its focal plane, the instrument holds an array of 14 electronic

detectors, each covered by a filter in one of three wavelength bands: 400 to 600

nanometers (blue-green), 550 to 850 nanometers (red), or 800 to 1000 nanometers

(near infrared). Ten red detectors are positioned in a line totaling 20,028 pixels across

to cover the whole width of the field of view. Two each of the blue-green and near-

infrared detectors lie across the central 20 percent of the field. Pixel size in images

taken from an altitude of 300 kilometers (186 miles) will be 30 centimeters (12 inches)

across, about a factor of two better than the highest-resolution down-track imaging

possible from any earlier Mars orbiter and a factor of five better than any extended

imaging to date. As a rule of thumb, at least three pixels are needed to show the shape

of a feature, so the smallest resolvable features in the images will be about a meter (3

feet) across for an object with reasonable contrast to its surroundings. The instrument

uses a technology called time delay integration to accomplish a high signal-to-noise

ratio for unprecedented image quality. 

Dr. Alfred McEwen of the University of Arizona, Tucson, is the principal investigator for

the High Resolution Imaging Science Experiment. Ball Aerospace, Boulder, Colo., built

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