DOI: 10.5061/dryad.p2ngf1w0v
title: Data from: Interannual and seasonal changes in the south seasonal polar cap of Mars: Observations from MY 28-31 using MARCI

description: This data set collects contours for the seasonal cap retreat published in
 Figure 3 of the associated article in Icarus. There are two zip files, one
 for text and one for shapefiles.  See the methods for how to
 convert pixel locations to lat/lon coordinates. The Mars Color Imager
 (MARCI) camera on the Mars Reconnaissance Orbiter provides daily synoptic
 coverage that allows monitoring of seasonal cap retreat and interannual
 changes that occur between Mars Years (MY) and over the southern summer.
 We present the first analysis of this data for the southern seasonal cap
 evolution observed in MY 28, 29, 30 and 31 (2/2007 to 07/2013).
 Observation over multiple Mars years allows us to compare changes between
 years as well as longer-term evolution of the high albedo deposits at the
 poles. Seasonal cap retreat is similar in all years and to retreats
 observed in other years by both optical and thermal instruments. The
 cryptic terrain has a fairly consistent boundary in each year, but
 numerous small-scale variations occur in each MY observed. Additionally,
 numerous small dark deposits are identified outside the classically
 identified cyptic region, including Inca City and other locations not
 previously noted. The large water ice outlier is observed to retain
 seasonal frost the longest (outside the polar dome) and is also highly
 variable in each MY. The development of the cryptic/anti-cryptic
 hemispheres is inferred to occur due to albedo variations that develop
 after dust venting starts and may be caused by recondensation of CO2 ice
 on the brightest and coldest regions controlled by topographic winds.
 Ground ice may play a role in which regions develop cryptic terrain, as
 there is no elevation control on either cryptic terrain or the late season
 brightest deposits.
description: The data are strored as region of interest (ROI) text or evf
 shape files saved from the software ENVI.  Each subfolder includes a png
 image of the contours over MOLA elevation.  For the text files, each ROI
 is stored sequentially, the header notes the number of points in each ROI
 and then provides an x, y value for each point in the ROI. There are 12
 ROIs for each year, every 10 degrees of Ls from 205 to 315. To convert
 these to lat lon, the image is a polar stereo projection 720 x 720
 pixels.  These reach 60 deg latitude at the edges of the frame, there are
 lower latitudes in the corners. 0,0 is the upper left by the Argyre impact
 basin and 720,720 the lower right.  The center of the image (360,360) is
 the south pole(90S, 0). Use the pixel coordinate to determine the distance
 from the center of the image, this radial distance in converted to
 latitude using 30 deg/360 pixels. Longitude is similarly calculated using
 the angle from center top, which is 0 degrees with E quadrants note in
 Figure 1 of the associated Icarus article.
description: Data from: Interannual and seasonal changes in the south seasonal polar
 cap of Mars: Observations from MY 28-31 using MARCI
 [https://doi.org/10.5061/dryad.p2ngf1w0v](https://doi.org/10.5061/dryad.p2ngf1w0v) ## Description of the data and file structure MARCI image mosaics are used to track the retreating seasonal cap over the south pole of Mars. See methods for converting point values to latitude and longitude. ### Files and variables #### File: 4MY\_contours\_ROI\_Text.zip **Description:**  This zip file includes contours for 4 Mars Years at 5 values of Ls. **Files in this zip archive** * 4MY_5Contours_Thick.png * 4MY_5Ls.txt * mola_s32_MARCIproj.png * mola_w_grid.jpg * My28_2007_StdColors.txt * My29_2009_StdColors.txt * My30_2011_StdColors.txt * My31_2013_StdColors.txt **Description of Files** ***4MY_5Contours_Thick.png*** * PNG format image file showing color contours at Ls 205, 235, 265, 295, 315 * Colors are MY28 (green), MY29 (magenta), MY30 (blue), MY31 (cyan) ***4MY_5Ls.txt*** * ; Header describes number of ROIs and number of points in each ROI * ; ROI points stored as Point ID, X, Y, Band * ``` XXXX XXX XXX XXX ``` * Each set of ROI points is separated by a blank line and the next ROI begins over with point 1 ***mola_s32_MARCIproj.png*** * Base MOLA elevation in grayscale at the same projection as MARCI images used to derive the contours ***mola_w_grid.jpg*** * Base MOLA elevation in grayscale at the same projection as MARCI images used to derive the contours with lat/lon grid ***My28_2007_StdColors.txt*** ***My29_2009_StdColors.txt*** ***My30_2011_StdColors.txt*** ***My31_2013_StdColors.txt*** * These four text files follow the same format * File title notes Mars Year of data contour * ; Header describes 12 ROIs and number of points in each ROI * ; ROI points stored as Point ID, X, Y * ``` XXXX XXX XXX ``` * Each set of ROI points is separated by a blank line and the next ROI begins over with point 1 * 12 ROIS correspond to Ls 205, 215, 225, 235, 245, 255, 265, 275, 285, 295, 305, 315 #### File: MY28\_31\_S\_Retreat\_Shapefiles.zip **Description:** This zipfile include one folder for each Mars year. The structure of each folder uses the same format with contours stored as .evf files and a .png image of the contours over MOLA elevation. **Folders in this zip archive** * My28_Shapefiles * My29_Shapefiles * My30_Shapefiles * My31_Shapefiles **Files in each folder** * Ls205.evf * Ls215.evf * Ls225.evf * Ls235.evf * Ls245.evf * Ls255.evf * Ls265.evf * Ls275.evf * Ls285.evf * Ls295.evf * Ls305.evf * Ls315.evf * Myxx_contours_thick.png ## Code/software Shapefiles were created in ENVI and may not be compatible with other GIS software as they are points, not geolocations. ## Access information Other publicly accessible locations of the data: * N/A Data was derived from the following sources: * MARCI camera on board the Mars Reconnaissance Orbiter