Mars is a very diverse and interesting place that has captured the human imagination for generations. Evidence continues to indicate that Mars has had a very active hydrological cycle over its history. The University of Arizona-led Phoenix lander has found ice just under the surface at high northern latitudes on Mars. Enormous flood channels much larger than anything on Earth reveal that liquid water existed on the surface, if only briefly, and may have flowed into a shallow ocean at northern high latitudes. It is now understood that Mars obliquity varies from ~5o to 45o over million year time scales dramatically altering the latitudinal distribution of solar heating. Based on evolving geological evidence and modeling results, this heating apparently drives dramatic changes in the distribution of surface water which apparently moves from high latitudes during present conditions to low latitudes at high inclinations. It is not clear if the hydrological cycle in the present climate is in equilibrium or if it is evolving slowly.
Critical to understanding past (and future) behavior is understanding the present hydrological cycle and the processes controlling it. As with Earth, I am very interested in the Martian hydrological cycle and using our ideas developed for Earth to measure and reveal its many secrets.
William Folkner (JPL) and I conceived the Mars Atmospheric Climate Observatory (MACO) in 2001 in response to NASAs Mars Scout PI-led mission announcement of opportunity. MACO centers around satellite to satellite radio occultation measurements (like ATOMMS) to profile the atmosphere plus shorter observations to measure dust and aerosols. MACO was one of 10 missions selected to receive funding from NASA to develop our concept (http://www.spacedaily.com/news/mars-scouts-01b2.html). The MACO science concept as defined after the first Mars Scout opportunity is summarized in Kursinski et al., (2004).
We developed the MACO concept in preparation for the first Mars Scout opportunity in 2002 but could not stay within the budget. We expanded, refined and submitted a MACO proposal for the 2nd Mars Scout announcement in 2006 for a 2011 launch where it received excellent science reviews but was not selected.
MACO to determine the water cycle as it exists currently on Mars, constraining the physical processes needed to create models to determine how the cycle likely behaved in the past. It also was to determine how Mars dust storms initiate, evolve and decay using MACOs unique ability to simultaneously observe dust and water cycle interactions. MACO would determine isotopic variations in water due to phase changes and photochemistry to address questions about the past evolution of the Martian atmosphere and the distribution of atmospheric methane & other key trace gases and their source regions
1) First global mapping of the four dimensional evolution of water vapor & ice (lat, lon, height, and local time) as a function of season
2) Direct measurement of meridional water transport, including answering the question of net pole-to-pole water transport
3) Unique ability to simultaneously observe dust and water cycle interactions
4) Direct measurement of surface-atmosphere water exchange over entire planet
5) Identify near-surface ancient water reservoirs
6) Determine isotopic variations in water due to phase changes and photochemistry
7) Identify atmospheric methane & other trace gases and look for source regions
8) Establish importance of heterogeneous chemistry processes and dust charging
The mission centers around satellite to satellite mm-wave occultations and passive measurements supplemented by other instruments operating at IR and visible wavelengths that provide key information on aerosols and symmetric molecules that the mm-wave observations cannot provide. In many ways, MACO is designed as a global field campaign where I drew upon objectives and instrumentation associated with water-related field campaigns on Earth. The instrument suite consisted of
A. mm-wave Limb Sounder (MMLS) MMLS is the Martian version of our Earth-based ATOMMS instrument that would profile water vapor and HDO, temperature, pressure, winds, trace species such as O3, H2O2 , SO2 and OCS and turbulence.
B. Mars Ice and Dust Sounder (MIDS) MIDS is a thermal IR sensor based on MCS that is designed to sense dust and ice aerosols, critical to Mars climate. I co-developed the MIDS concept and design with Tim Schofield (JPL) and Erick Young (UA) to complement the aerosols-insensitive MMLS instrument.
C. Solar Occultation in the Infra-Red (SOIR) [France, PI: Franck Montmessin] The near-IR solar occultation, grating spectrometer instrument of Jean-Loup Bertoux and Franck Montmessin was added to MACO to observe methane as well as other constituents. Definitive detection of methane would strongly suggest recent biogenic or magmatic activity because of methanes 300-year photochemical lifetime in the Martian atmosphere.
D. Frost and Atmospheric Water Spectrometer (FrAWSt) [France/Russia, PI: Oleg Korablev] FrAWSt was added to provide a method of measuring the presence of water frost below each occultation profile to constrain and understand exchange of moisture between the atmosphere, surface and subsurface.
E. Limb Imaging of Mars by Occultation (LIMO) [Canada, PI: Peter Bernath] LIMO, an existing Canadian instrument on the Earth-orbiting Atmospheric Chemistry Experiment (ACE), was to determine aerosol extinction profiles at 0.5 and 1 microns via solar occultation to constrain the aerosol properties, particularly the particle size distribution.
MACO is an unprecedented remote sensing mission focused on the Martian water cycle as well as determining the trace gas inventory and answer questions such as the existence of methane in the Martian atmosphere. With 2-satellite occultation measurements supplemented by others at shorter wavelengths, MACOs global weather and climate observing system concept for Mars essentially represents how one would develop a global remote sensing system without using a balloon (radiosonde) sounding network.
MACO received excellent reviews for the science concept including recognition of the fact that there was no other way of doing much of what MACO was doing but MACO, as proposed, was deemed high risk and was therefore not selected.
While not selected in 2006, MACO remains a revolutionary remote sensing mission concept that should be implemented to understand the climate and trace chemistry of Mars as well as provide a very quantitative data set for comparison with Earth. As Jack Mustard, current head of the Mars Exploration Program Analysis Group (MEPAG), indicated in a recent e-mail exchange, MACO sounds wonderful and has the precision and measurement capabilities we are certainly dreaming of for the next round of atmospheric measurements for Mars.
The two spacecraft needed to perform the perform satellite-to-satellite occultations Fitting MACO into a Scout budget is likely to be viewed as risky because MACO requires to. MACO is therefore better suited to a mainstream Mars mission slot with a significantly larger budget like that designated for the Mars Science Orbiter (MSO) whose scientific objectives and measurement capabilities are actually a subset of those of MACO. MACO can achieve the MSO objectives and more, complete with functionally similar instruments such as the Canadian solar occultation FTIR presently in orbit around Earth but with far much better vertical resolution and accuracy than the microwave portion of MSO. We continue to push the MACO concept as the next major Mars atmospheric mission likely in 2018, working with MEPAG to consider the capabilities of MACO in their MSO-related science analysis.
In preparing the MACO proposal in 2006, we brainstormed and performed a number of innovative studies to assess what MACO could deliver in terms of observations and science. This process yielded a truly revolutionary mission concept that generated an unusual level of excitement from science reviewers as reported by Michael Meyer at NASA HQ. Several of us on the MACO team have spent an enormous amount of time since 2001 on defining, developing and refining the MACO concept. However, MACO remains minimally documented in the form of the MACO proposal submitted in 2006 and the 2004 OPAC1 paper which is now somewhat out of date because of the innovations developed in the 2006 proposal. We have been hesitant to document our innovations in the peer-reviewed literature because of the inherently competitive nature of the Mars Scout program.
Now that I have decided recently that MACO has a significantly higher likelihood of being implemented as a mainstream Mars mission rather than as a competitive Mars Scout mission, it is clear that these innovations need to be documented in the peer-reviewed literature.
The following is a list of papers that will describe the MACO innovations.
Kursinski, E. R., P. Elosegui, M. Gurwell, D. Ward and D. Wu, Profiling Martian winds from orbit.
This paper will document the contributions and quantify the performance of the 4 methods used by MACO to measure winds from orbit: measuring the wind-induced Doppler shift of absorption lines via satellite to satellite occultations, solar occultation and passive emission and indirectly inferring winds via horizontal pressure gradients. The combined capabilities are truly remarkable and far better than any capability orbiting Earth.
Kursinski, E. R,. A. Otarola, D. Ward, R. Frehlich, J. Barnes and D. Tyler, Remote sensing of turbulence in the atmosphere of Mars.
This will document our study done combining Large Eddy Simulation (LES) model output (see left figure above) from Jeff Barnes and Dan Tyler at Oregon State U.
and our understanding of turbulence developed for ATOMMS. This study determined that the MACO satellite-to-satellite occultations provide the sensitivity and
vertical resolution to profile near-surface turbulence and the diurnal evolution of the boundary layer (see right figure above).
This is critical to understanding the exchange of energy, momentum and constituents between the atmosphere and surface as well as to support spacecraft Entry, Descent and Landing (EDL).
Kursinski, E. R., J. McConnell, and M Richardson, Remotely and globally determining Martian water exchange between the surface and atmosphere.
This documents a study we did with Jack McConnell at York Univ. in Canada. Jack provided output of model diurnal variations in temperature (top row of figures above)
and water vapor (bottom row of 2 figures above) in the lowest 2 km of the Martian troposphere. From these and knowledge of the MACO satellite to satellite occultation
vertical resolution and sensitivity, we determined that the precision and the better than 100 m vertical resolution of the MACO satellite to satellite occultation profiles of
water vapor and temperature will accurately measure these diurnally varying signatures including the very shallow nocturnal boundary layer that becomes depleted of
water by diffusion of water vapor into the surface. Observing the temporal evolution of this boundary layer (which would be measured over about 40 days via the
rapidly precessing orbits) is key to understanding how water diffuses into and out of the subsurface at different locations around the globe.
Determining the exchange of water between the surface and atmosphere and the resulting implications of depth of water under the surface create
in a very real sense a global version of the present Phoenix lander mission and critical to selecting future landing sites.
Kursinski, E. R., A. Otarola, J. T. Schofield and C. Newman, Remotely sensing the genesis and evolution of Martian dust storms.
This will document the design and capabilities of MACO instruments, particularly MMLS and MIDS, to globally profile dust, stability and winds and answer key questions about the evolution of Martian dust storms.
Kursinski, E. R., M. Richardson, and W. Folkner, The Mars Astrobiology Climate Observatory (MACO): Determining the Martian hydrological cycle and climate.
This will be an overview of the mission science objectives and design related to climate. Another paper will likely be written about the trace chemistry capabilities of MACO.