Dao, Niger, and Harmakhis Vallis
Image Title: Dao, Niger, and Harmakhis Vallis
Source: Mars Global Surveyor
Located in the southern hemisphere of Mars, just east of the vast Hellas Planitia impact basin, are a trio of valleys that run from the southwest to the northeast. The location of the individual valleys is shown in Figure 1. Note that if you are using the NASA Atlas of Mars 1:5,000,000 Map Series book to look up this image, the labels that identify Dao and Harmakhis Vallis have been reversed.
Figure 1. Image Key.
A = Dao Vallis
B = Niger Vallis
C = Harmakhis Vallis
D = Poti Crater
E = Coronae Mons
Niger Vallis begins on the southern flank of the Martian volcano Hadriaca Patera and runs to the southwest. Dao Vallis is the downstream extension of Niger Vallis and is approximately 1,200 kilometers long. Harmakhis Vallis runs approximately parallel to Dao Vallis and is some 800 kilometers long. For all three valleys the downstream direction is from northeast to southwest (top to bottom in the image). It is thought that these valleys were formed during the Hesperian Epoch by running water. Given the proximity of the head end of these valleys to volcanoes and the relative ages, as well as the fact that all three valleys begin in an area of collapsed depressions, volcanic melting of subsurface ice is the leading contender as the source of water. However, what the maximum rate of flow was and how long it flowed are undetermined.
I created this image a few years ago to illustrate differing perspectives on the color of Mars as part of an educational presentation. The NASA MSSS version of this image can be seen at the JPL Planetary Photojournal web site. My version was meant to have a color feel reminiscent of the previous Viking color images of Mars.
Source Image Background
This image was created by merging two Mars Global Surveyor Wide Angle Camera frames: one taken using the blue filter and the other using the red filter. The green channel for the image was created by synthesizing a green image by combining the red and blue images and averaging them together. For more information on this process, you may want to read the article What Color is Your Planet. The original MGS image was taken in September 2000 when it was mid-autumn in the southern hemisphere of Mars. For purposes of comparison, you can see the official NASA version of this image at http://photojournal.jpl.nasa.gov/catalog/PIA02810.
All processing of this false color image was done with Adobe Photoshop using the techniques outlined in the article What Color is Your Planet.
I have created a low resolution version of Dao, Niger, and Harmakhis Vallis for use as a desktop wallpaper. In order to avoid cropping of the original image, I have altered the aspect ratio of this image. I am making this wallpaper available for your personal use only. It is not to be modified or redistributed in any form by any means. All rights are retained by the artist.