What three new USGS maps reveal about Mars | Hacker News Reader

What three new USGS maps reveal about Mars

usgs.gov

71 pointszdw10 comments

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Links to download the maps themselves:

Olympus Mons: https://www.usgs.gov/maps/geologic-map-olympus-mons-caldera-...

Aeolis Dorsa: https://www.usgs.gov/maps/geologic-map-aeolis-dorsa-region-m...

Athabasca Valles: https://www.usgs.gov/maps/geologic-map-athabasca-valles-regi...

Is geography on another celestial body still called geography?

I would think maybe astrogeography?

Areography in this case.

Yes. 'Geo', or in modern Greek γη (gi), means earth in the sense of land, not as the planet. Hence 'geology' is literally translated to 'earth/land study'. The science of geology is largely concerned with the structural study of the planet Earth, however it doesn't preclude the study of other celestial/astronomical objects. Geologists, for instance, will be studying data from the samples taken on Mars.

What an intensely irritating article.

The maps have all sorts of colored and textured areas with no hint of a legend to suggest what any mean. The text says the high point of O. Mons is in a surprising place while offering no hint where that is. Almost all the contour lines are unlabeled. Is the high point near the "21000" line? How much elevation is there between lines? Is the number meters? Meters above what? (No, not sea level.)

It says there are ridges where rivers used to be, with no hint how a river course could turn into a ridge.

Have you ever read those irritating comments on HN where they assume all manner of domain knowledge like bits, bytes, containers, .. etc?

Who'd have thought articles from the United States Geological Survey would expect some modicum of knowledge about geology?

Anyhow, here we go - rivers cut courses through soft substances, light sands, etc ..

Rivers carry heavy sediments from eroding hard objects upstream, clays, metals, granites, etc.

Rivers dry up and leave a heavy hardening layer at the bottom of their former course.

Light sands dry up and blow away .. leaving the former course of the river as a higher ridge of harder material different to the surrounding layers.

There are, of course, many other geologic processes that can result in similar features, many of these are covered in introductory geology books and classes.

WRT Maps:

The linked maps have image and metadata components, and full wall display integrated map sheets with legends.

eg Scientific Investigations Map 3470 (aka Sim3470), Geologic Map of Olympus Mons Caldera, Mars [1]

has quite a detailed breakdown of the colours and their meanings.

[1] https://pubs.usgs.gov/sim/3470/sim3470_sheet.pdf

Thank you. More broadly, when a credible source irritates with conciseness, that's a font for exploration, not complaining the wine wasn't chilled appropriately.

I think the question to be asking is who the intended audience for this article is.

It's worded in a way that seems to be for the layman, but the map snippets featured in the article convey no useful information because of the aforementioned lack of legends.

The arcgis maps linked to in the article, on the other hand, have a full legend and are fully interactable. Plenty useful for both laymen and experts alike.

I think the article could be presented better so there's less dissonance in its intention.

It would have sufficed to put the legend in as one of the in-line images.

When looking with my phone, the big PDF does not display.

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