Active Processes:  Bright Streaks and Dark Fans
NASA/JPL/University of Arizona
Active Processes: Bright Streaks and Dark Fans
PSP_002622_0945  Science Theme: Seasonal Processes

This caption is part of a December 2007 AGU presentation "Spring at the South Pole of Mars."

In a region of the south pole known informally as "Ithaca" numerous fans of dark frost form every spring. HiRISE collected a time lapse series of these images, starting at Ls = 185 and culminating at Ls = 294. "Ls" is the way we measure time on Mars: at Ls = 180 the sun passes the equator on its way south; at Ls = 270 it reaches its maximum subsolar latitude and summer begins.

In the earliest image fans are dark, but small narrow bright streaks can be detected. In the next image, acquired at Ls = 187, just 106 hours later, dramatic differences are apparent. The dark fans are larger and the bright fans are more pronounced and easily detectable. The third image in the sequence shows no bright fans at all.

We believe that the bright streaks are fine frost condensed from the gas exiting the vent. The conditions must be just right for the bright frost to condense.Written by: Candy Hansen  (12 December 2007)
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Acquisition date
16 February 2007

Local Mars time:
17:46

Latitude (centered)
-85.211°

Longitude (East)
181.474°

Range to target site
246.9 km (154.3 miles)

Original image scale range
49.4 cm/pixel (with 2 x 2 binning) so objects ~148 cm across are resolved

Map projected scale
50 cm/pixel

Map projection
Polarstereographic

Emission angle:
1.7°

Phase angle:
89.0°

Solar incidence angle
88°, with the Sun about 2° above the horizon

Solar longitude
185.1°, Northern Autumn

For non-map projected images
North azimuth:  121°
Sub-solar azimuth:  34.0°
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non-map           (250MB)

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non-map           (195MB)

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RGB color
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EDR products
HiView

NB
IRB: infrared-red-blue
RGB: red-green-blue
About color products (PDF)

Black & white is 5 km across; enhanced color about 1 km
For scale, use JPEG/JP2 black & white map-projected images

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All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible:
NASA/JPL/University of Arizona

POSTSCRIPT
NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA’s Science Mission Directorate, Washington. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.