Emily LakdawallaMar 04, 2014

A new map of Mars from some pretty old data

I have often mentioned that the best global color map of Mars that we have is, surprisingly enough, based on Viking Orbiter data from the 1970s. Well, that best global color map has recently been improved. Last month I discovered that the United States Geological Survey had released a new digital map product: the Colorized Viking Mars Digital Image Model (MDIM) version 2.1. It's better than the previous version in two ways: positions of individual features are more accurate, and the color has been corrected. Both corrections were made with the help of the Mars Orbiter Laser Altimeter's terrific topographic maps of Mars. So now the registration between the best topographic map and the best color map is perfect. Here's the map, at reduced resolution.

Color map of Mars: Viking Orbiter MDIM 2.1
Color map of Mars: Viking Orbiter MDIM 2.1 This is the most accurate color global mosaic of Mars to date, produced in 2014, from Viking data: the Viking Orbiter Colorized Mars Digital Image Model (MDIM) version 2.1. The click-to-enlarge version has a resolution of 2.5 km/pixel; the full-resolution map, available from the USGS, is 256 pixels per degree (232 m/pixel).Image: NASA / JPL / USGS

Thanks to Fred Calef for downloading the original 12-GB data set and producing this lower-resolution but still-awesome version for me. The USGS posted it in .cub format, which is the native format of their own geographic-reprojection software called ISIS.

It's gorgeous, although not perfect. For instance, there are clouds in Hellas basin (the white smudge south of the equator), and when you zoom way in to it, you do find some obvious seams. This is a product processed in a mathematically rigorous way, for scientific purposes, of a planet whose appearance changes over time, so seams are impossible to avoid. But it's still lovely when used for the right purposes.

So, what is this new map product good for? One thing is serving as a base for global maps. So I've updated my map of Mars landing sites with this new base map:

Map of all Mars landing sites as of November 2018
Map of all Mars landing sites as of November 2018 EDITOR'S NOTE: This infographic is current as of November 2018. An updated version is available here. This map represents the best known positions for all Mars landers, successful, failed, and planned. Gridlines are spaced 10 degrees apart, with 0 longitude at the center. White text denotes successful missions; gray text, failed missions; blue text, future missions.Image: NASA / JPL-Caltech / USGS (image); Emily Lakdawalla (map)

It's also super for producing simulated views of Mars from many perspectives, especially when used in combination with the global topographic data set. This is not work I can do myself, so I asked Doug Ellison at JPL if he'd seen the new map yet, and if he wanted to try playing with creating oblique global views like the "Daybreak at Gale crater" one that I have seen at the beginning of a gazillion slide presentations. To my delight, he thought that was a good idea, and made some really awesome new perspective views of different spots on Mars, so hopefully we will now see more variety in the opening slides of Mars sceince presentations!

My personal favorite is this view on Gusev Crater -- erstwhile home to Spirit's mission -- and the neighboring Apollinaris Mons:

Perspective view of Mars: Apollinaris Mons, Gusev Crater, and Ma'adim Vallis
Perspective view of Mars: Apollinaris Mons, Gusev Crater, and Ma'adim Vallis The straight, steep-sided channel of Ma'adim Vallis enters the flat-floored Gusev crater from the south in this perspective view of Mars generated from Mars Global Surveyor topographic data and Viking orbiter color data. To the north (left) of Gusev is a volcano, Apollinaris Mons. The Mars Exploration Rover Spirit performed its mission within Gusev crater from January 2004 to March 2010.Image: NASA / JPL-Caltech / USGS / MOLA Science Team

Here's a nice view onto some of Mars' outflow channels, which also happens to include the landing sites of Viking 1 and Pathfinder:

Perspective view of Mars: Outflow channels, Viking 1 and Pathfinder landing sites
Perspective view of Mars: Outflow channels, Viking 1 and Pathfinder landing sites A perspective view on Mars employing Viking color data looks over Chryse Planitia, a smooth region of the planet into which many of Mars' outflow channels emptied. Two landers touched down in this part of the globe: Viking 1 (which landed near the mouth of Kasei Valles, near the terminator at left), and Pathfinder (which landed near the mouths of Tiu and Ares Valles, which flowed around the streamlined islands on the right).Image: NASA / JPL-Caltech / USGS / MOLA Science Team

But we keep coming back to Gale; its central mound makes it so easy to spot from space, and let's face it, there are going to be lots of slide presentations about Gale in the years to come, so let's make them some more variety in title slides:

Perspective view of Mars: Gale on the terminator
Perspective view of Mars: Gale on the terminator In this simulated view of Mars, Gale crater, with its characteristic central mound, is just rotating into sunlight. The Curiosity rover is pursuing its science mission on the north side of that mountain.Image: NASA / JPL-Caltech / USGS / MOLA Science Team

It's wonderful that, 40 years later, the data returned from the Viking mission is still valuable to scientists. Doug thought the same thing: "The data from older instruments doesn't become redundant, it becomes the backbone upon which each new instrument is targeted and its data correlated to." The same will be true for other missions that established the first complete surveys of neighboring worlds: like MESSENGER at Mercury, or Magellan at Venus.

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