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Ozone on Mars: Two Windows Better Than One


Understanding the present-day Martian climate gives us insights into its past climate, which in turn provides a science-based context for answering questions about the possibility of life on ancient Mars.

Our understanding of Mars’ climate today is neatly packaged as climate models, which in turn provide powerful consistency checks – and sources of inspiration – for the climate models which describe anthropogenic global warming here on Earth.

But how can we work out what the climate on Mars is, today? A new, coordinated observation campaign to measure ozone in the Martian atmosphere gives us, the interested public, our own window into just how painstaking – yet exciting – the scientific grunt work can be.

An illustration showing the ESA's Mars Express mission, launched in June 2003, in orbit around the planet (Credit: ESA/Medialab)


The Martian atmosphere has played a key role in shaping the planet’s history and surface. Observations of the key atmospheric components are essential for the development of accurate models of the Martian climate. These in turn are needed to better understand if climate conditions in the past may have supported liquid water, and for optimizing the design of future surface-based assets at Mars.

Ozone is an important tracer of photochemical processes in the atmosphere of Mars. Its abundance, which can be derived from the molecule’s characteristic absorption spectroscopy features in spectra of the atmosphere, is intricately linked to that of other constituents and it is an important indicator of atmospheric chemistry. To test predictions by current models of photochemical processes and general atmospheric circulation patterns, observations of spatial and temporal ozone variations are required.

The Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars (SPICAM) instrument on Mars Express has been measuring ozone abundances in the Martian atmosphere since 2003, gradually building up a global picture as the spacecraft orbits the planet.

These measurements can be complemented by ground-based observations taken at different times and probing different sites on Mars, thereby extending the spatial and temporal coverage of the SPICAM measurements. To quantitatively link the ground-based observations with those by Mars Express, coordinated campaigns are set up to obtain simultaneous measurements.

Infrared heterodyne spectroscopy, such as that provided by the Heterodyne Instrument for Planetary Wind and Composition (HIPWAC), provides the only direct access to ozone on Mars with ground-based telescopes; the very high spectral resolving power (greater than 1 million) allows Martian ozone spectral features to be resolved when they are Doppler shifted away from ozone lines of terrestrial origin.

A coordinated campaign to measure ozone in the atmosphere of Mars, using SPICAM and HIPWAC, has been ongoing since 2006. The most recent element of this campaign was a series of ground-based observations using HIPWAC on the NASA Infrared Telescope Facility (IRTF) on Mauna Kea in Hawai’i. These were obtained between 8 and 11 December 2009 by a team of astronomers led by Kelly Fast from the Planetary Systems Laboratory, at NASA’s Goddard Space Flight Center (GSFC), in the USA.

Credit: Kelly Fast


About the image: HIPWAC spectrum of Mars’ atmosphere over a location on Martian latitude 40°N; acquired on 11 December 2009 during an observation campaign with the IRTF 3 m telescope in Hawai’i. This unprocessed spectrum displays features of ozone and carbon dioxide from Mars, as well as ozone in the Earth’s atmosphere through which the observation was made. Processing techniques will model and remove the terrestrial contribution from the spectrum and determine the amount of ozone at this northern position on Mars.

The observations had been coordinated in advance with the Mars Express science operations team, to ensure overlap with ozone measurements made in this same period with SPICAM.

The main goal of the December 2009 campaign was to confirm that observations made with SPICAM (which measures the broad ozone absorption spectra feature centered at around 250 nm) and HIPWAC (which detects and measures ozone absorption features at 9.7 μm) retrieve the same total ozone abundances, despite being performed at two different parts of the electromagnetic spectrum and having different sensitivities to the ozone profile. A similar campaign in 2008, had largely validated the consistency of the ozone measurement results obtained with SPICAM and the HIPWAC instrument.

The weather conditions and the seeing were very good at the IRTF site during the December 2009 campaign, which allowed for good quality spectra to be obtained with the HIPWAC instrument.

Kelly and her colleagues gathered ozone measurements for a number of locations on Mars, both in the planet’s northern and southern hemisphere. During this four-day campaign the SPICAM observations were limited to the northern hemisphere. Several HIPWAC measurements were simultaneous with observations by SPICAM allowing a direct comparison. Other HIPWAC measurements were made close in time to SPICAM orbital passes that occurred outside of the ground-based telescope observations and will also be used for comparison.

The team also performed measurements of the ozone abundance over the Syrtis Major region, which will help to constrain photochemical models in this region.
Analysis of the data from this recent campaign is ongoing, with another follow-up campaign of coordinated HIPWAC and SPICAM observations already scheduled for March this year.

Putting the compatibility of the data from these two instruments on a firm base will support combining the ground-based infrared measurements with the SPICAM ultraviolet measurements in testing the photochemical models of the Martian atmosphere. The extended coverage obtained by combining these datasets helps to more accurately test predictions by atmospheric models.

It will also quantitatively link the SPICAM observations to longer-term measurements made with the HIPWAC instrument and its predecessor IRHS (the Infrared Heterodyne Spectrometer) that go back to 1988. This will support the study of the long-term behavior of ozone and associated chemistry in the atmosphere of Mars on a timescale longer than the current missions to Mars.

Sources: ESA, a paper published in the 15 September 2009 issue of Icarus

Comments on this entry are closed.

  • Aqua February 20, 2010, 3:25 PM

    “… constrain photochemical models in this region.” Is a most interesting statement! indicating exact/precise measurements of the solar wind as cold fusion chemosynthesis driver?

  • Jon Hanford February 20, 2010, 6:06 PM

    I seem to remember a recent study done of a transiting exoplanet in which emission was sought that may have resulted in detectable auroral-type activity using either XMM-Newton or Chanda. Null results were obtained but upper parameters were set wrt the phenomena. Perhaps others have more detailed info?

  • Jon Hanford February 20, 2010, 6:45 PM

    I manged to find this poster (current to 2008) on “Magnetospheric Emission from Extrasolar Planets” here:

    http://arxiv.org/abs/0903.0873

  • Torbjorn Larsson OM February 21, 2010, 5:07 AM

    Especially painstaking if Mars climatologists harken to the same 30 year climate definition as I believe Earth climatologists use. That 1988 data may seem old but would suffice to establish some baseline. (The models themselves are different business I guess.)

    [OT and personal, but this resonates hugely for me right now. Not only am I immersed in an atmosphere (no pun intended) of astrophysicist dealings, I’ve just started to do software prep for a campaign that may happen next year. [Don’t ask, I dunno how that happened. But it’s fun!]

    First order of business after resetting the tripped ground current leakage protector (what, the reactive load of a 10 A @ 220 V supply a lot, you gotta be kidding me :-o) was to unplug and fix the VXI casing feet that also turned out a mess. Rough grunts, if you ask me.

    And I’m pretty sure none of that qualifies as software work in the purest sense. So at best I’m now a grunt as well. :-D

    … I’ll better get my coat and see myself out. Ta!]

  • Aqua February 21, 2010, 8:59 AM

    Its interesting to note the aurora’s seem to form over the darker, more exposed and denser basaltic deposits, which are more conductive, geomagnetically and gravitationally speaking…?

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