[GrendelRex]

I'm trying to find a book that I began to read about 10 years ago --- it was published sometime in the last 25 years or so.

What I remember is that signs of alien life/technology had been found on Mars. The United States had been out maneuvered by the other major countries of Earth, who had laid claim to the "Artifact Zones" of Mars.

Does this ring a bell for anyone?

Semper Mars by Ian Douglas ? It's part of his Heritage trilogy.

[GrendelRex]

I found a copy of "Semper Mars" and read the first couple of chapters. While similar, this isn't the one I remember. The one I'm trying to find had the United States with a more bleak situation. Other countries had gotten to Mars ahead of the US (IIRC) and laid claim to the "Artifact Zones" ahead of us. I do remember that that's how they were actually called in the beginning of the novel.

"Semper Mars" will definitely go in my "to read" pile, though.

There are actually a lot of SF novels taking place on Mars and the alien artifacts trope is rather common too. I have googled "artifact zones" and can't seem to find anything related to your novel.

Here are a few links about SF literature with Mars as a setting. Try and check them and you might find it (use Goodreads to read a synopsis/summary of each title if you need it) :
http://scifan.com/themes/mars/marsbiblio.asp
http://www.irosf.com/q/zine/article/10021
https://www.goodreads.com/list/show/302.100_Science_Fiction_and_Fantasy_Books_set_on_or_about_Mars
http://www.sf-encyclopedia.com/entry/mars
http://en.wikipedia.org/wiki/Mars_in_fiction
https://www.kirkusreviews.com/features/mars-science-fiction-part-1/
http://sffbooksonmars.blogspot.fr/

You can also use the Internet Speculative Fiction Database (ISFDB) which allows you to search books by tags.
Examples of tag search :
Mars : http://www.isfdb.org/cgi-bin/tag.cgi?1281
Earth-Mars War : http://www.isfdb.org/cgi-bin/tag.cgi?5315
Alien Artifact : http://www.isfdb.org/cgi-bin/tag.cgi?1061
Artifact : http://www.isfdb.org/cgi-bin/tag.cgi?1231

Librarything has a similar search function if that can help.
Mars : https://www.librarything.com/tag/Mars
Artifact : https://www.librarything.com/tag/artifact
Alien Artifact : https://www.librarything.com/tag/alien+artifact

[Tidal]

@oneeyed, that is such a helpful post! Gathering those links would have taken not a little time and patience. Though I didn't make the initial inquiry, am sure I'll be able to use those links to good purpose in the future. Thank you!

[GrendelRex]

After checking a few of the suggestions, the one I was searching for remains unknown. Thanks for all responses --- they are much appreciated

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