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Mars Climate Sounder Science Objectives

Click to enlarge >

Mars Climate Sounder will be the first science investigation at Mars that is capable of performing a "4-dimensional" study (three spatial dimensions and time) of the key properties of Mars' atmosphere.  Throughout an entire Martian year (and hopefully longer), Mars Climate Sounder will almost continuously acquire vertical profiles of the temperature, pressure, dust, and clouds of the lower 80 kilometers (50 miles) of Mars' atmosphere, everywhere along Mars Reconnaissance Orbiter's polar orbit.  The extensive data set will enable Mars climatologists to follow water and carbon dioxide around Mars, from their sources in the polar caps (and possibly elsewhere), to different levels in the atmosphere, to their sinks again in the polar caps (and possibly elsewhere), as the Martian seasons wax and wane.

Mars scientists have wanted to perform this kind of detailed, systematic study of Mars' climate for decades, but they have been foiled -- twice -- by the loss of the spacecraft that were carrying Mars Climate Sounder's precursors to Mars.  The precursor, called PMIRR (Pressure Modulator Infrared Radiometer), was first launched with Mars Observer in 1992, but Observer disappeared without a trace just 3 days before orbit insertion.  A duplicate, PMIRR II, was of central importance on the Mars Climate Orbiter, launched in 1998.  That spacecraft was lost upon orbit insertion.  For Mars Reconnaissance Orbiter, the PMIRR team started over with a completely redesigned instrument, now called Mars Climate Sounder, but the science objectives have remained the same.

The Science Objectives

The science investigations on space missions are guided by a few stated science objectives.  The mission has one set of objectives.  Each science instrument may contribute data toward the study of just one or many of these objectives.  Each instrument has its own, more specific science objectives.  Finally, each instrument has a stated set of measurements it plans to perform to gather the data set that scientists believe will be required to meet those science objectives.

Mars Reconnaissance Orbiter has three main objectives:

• 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.
• Identify sites where possible effects of liquid water indicate environments that may have been conducive to biological activity or might even now harbor life.
• Identify and characterize sites for future Mars landings.

Mars Climate Sounder will focus on the first of these three objectives.  Mars Climate Sounder has its own, more specific science objectives:

• Perform continuous and complete global monitoring of the properties of the atmosphere in order to study the atmospheric circulation, year-to-year variation in climate, and annual cycles in the distribution and abundance of water and dust.
• Measure the thermal properties of the surface and near-surface materials in order to study climate and the distribution and state of surface and subsurface water.
• Study the seasonal distribution of carbon dioxide clouds and frost in order to search for year-to-year trends in Mars' global climate.

To meet these goals, Mars Climate Sounder will make the following measurements:

• Map the three-dimensional and time-varying thermal structure of the atmosphere from the surface to an altitude of 80 kilometers.
• Map the distribution and quantity of dust in the atmosphere and how it varies over time.
• Map the vertical distribution of atmospheric water vapor to an altitude of at least 35 kilometers and how it varies over time.
• Determine which materials are forming clouds (water or carbon dioxide) and map how they vary in distribution over time.
• Map atmospheric pressure and how it varies with time and season.
• Monitor the temperature and quantity of reflected light coming from the surface of the poles and how it varies with time and season.

Continuous is Key

Click to enlarge > Example single-day temperature map from Mars Climate Sounder One of the data products that Mars Climate Sounder will be able to produce is daily maps of the temperature across the surface of Mars, much as the Thermal Emission Spectrometer (TES) team on Mars Global Surveyor did. The base map here is a one-day temperature map produced with TES data (15 µm temperatures from July 1, 2001). The black rectangles illustrate schematically the data gaps that would result from rolling Mars Reconnaissance Orbiter more than 9 degrees in order to point the cameras at interesting targets. Credit: NASA / JPL-Caltech / ASU / Tim Schofield

Many of the measurements that Mars Climate Sounder will perform have been performed in the past.  In particular, several landed Mars missions have acquired extremely detailed profiles of temperature and pressure as they descended to the surface, and these profiles have provided important inputs into climate models.  But no mission has been able to acquire this kind of information for all of Mars for all of a Martian year.

There will be a few interruptions in Mars Climate Sounder's data set.  For instance, whenever Mars Reconnaissance Orbiter rolls more than 9 degrees in order to point its high-resolution camera at an enticing target on the surface, Mars Climate Sounder will miss acquiring an atmospheric profile at that point.  These rolls will create unavoidable gaps in Mars Climate Sounder's coverage.  But every place on Mars will be measured repeatedly by Mars Climate Sounder, so, over time, all of these areas will be covered many times, building up the "four-dimensional" picture (3-D view of the atmosphere plus the dimension of time) that climate modelers seek.