Other Planet Science Concept Information Sheet
Break-out: Other Planet
Form completed by: Scot Rafkin
Concept title (ID): Water cycle of Mars (1)
Description of the potential science / science goals:
Observe and understand the processes behind the dynamic distribution of water on Mars through
synoptic observations of clouds, haze and frost.
1. Water exchange in atmosphere and surface reservoirs.
2. Climatology and variations of diurnal/season clouds and surface frosts
3. Water cycle connections to dust cycle (see Dust Cycle of Mars Concept)
Relevance of the science (Why is this important?) What are the specific Decadal ties?
The decadal survey calls out climate studies - past and present - as a major objective of Mars exploration
(p. 141). The dust, carbon dioxide and water cycles are mentioned specifically (p. 147 - 148). In addition,
the decadal survey lists two “important questions” (p. 150) that are addressed by this topic: what are
the processes coupling the CO2, dust and water cycles, and how does the climate, and especially the
water cycle, vary with orbital and obliquity variations. While the “obliquity” part of this question
pertains to long time scales, the resent-day water cycle can be observed over a full orbital cycle with
unique diurnal coverage from a balloon-borne telescope.
1.
2.
3.
4.
Mars prominently featured in the DS.
Water has astrobiological significance.
The atmosphere is the conduit through which water moves between its primary reservoirs.
Spacecraft are typically sun synchronous and do not provide diurnal coverage. Water ice clouds
are highly variable over the diurnal cycle; spacecraft strongly alias diurnal signals and harmonics
of diurnal period.
5. Seasonal variation requires periodic monitoring over the course of a Mars year.
What measurements are required to achieve the science?
Imaging in 2 - 5 filters between 0.4 - 1 µm (to distinguish dust from water clouds) at 0.1” resolution
(equivalent to 150 - 200 pixels across Mars’ disk at superior conjunction). This resolution is comparable
to the resolution used in many GCMs. Water is bright in the violet and UV. Contrast between blue-UV
wavelengths are red discriminate clouds from dust disturbances. 1” would provide spatial resolution up
to ~25 pixels or more across disk. IR emission might be feasible and could provide coverage during the
Mars night as well as day.
What are the driving requirements to achieve the measurements? (E.g. time on target, frequency of
observations, aperture, focal length, wavelengths, pointing precision and stability, specific observing location(s),
critical observation time(s), are repeat flights required? or whatever else that may drive the hardware or mission
design/architecture).
Telescope aperture: 1m nominal, sufficient for 50 km resolution on Mars at superior conjunction.
Telescope focal length: TBD
Wavelengths: Vis through Near UV, possible IR. 0.4 - 1 micron
Pointing precision: .05”
Required time on target: Even one day of continuous monitoring would provide coverage not presently
achievable. Longer duration increases the opportunity to capture more of the randomly occurring
disturbances. A flight every ~40 degrees of Ls (~80 earth days) would provide reasonably good seasonal
coverage. At end of northern Mars spring would be preferential (sun returns to North pole). A few
minutes per filter, repeated on a roughly hourly basis to monitor clouds throughout a martian day. Most
useful would be 100 days of hourly imaging of Mars at 0.1” resolution.
Are there other ways to achieve this science, and if so, why would a balloon platform be preferable?
No. Synoptic observations over all local times is not possible from orbit and ground-based facilities
cannot dedicate the necessary resources to do this.
Mars orbiters take high much higher resolution images than would be obtained from a balloon-borne
telescope, but a balloon has two critical advantages over a spacecraft in Mars orbit.
* Every image from a balloon can include Mars’ entire disk, and
* A terrestrial balloon can take a continuous stream of images at any cadence, as opposed to an orbiting
spacecraft which generally images a certain swatch of Mars at the same Martian time of day on every
orbital pass.
In other words, a balloon-borne telescope has the unique capability of imaging Mars’ entire disk
continuously throughout the martian day at resolutions comparable to that of GCMs, . A groundbased
telescope with adaptive optics could obtain similar resolutions in J-H-K bands, but only a long-duration
balloon mission could obtain images with an hourly cadence over a span of several months.
What are the potential observation targets?
Mars
What planetary science disciplines would this involve?
Mars atmosphere/climate/ geology/hydrology.
Point of contact for follow-on questions (Name and contact info)
Scot Rafkin
Southwest Research Institute
rafkin@boulder.swri.edu