The rovers have x-ray spectrometers to determine elemental compositions of Martian rocks and materials.
Ralf Gellert is the principle investigator for the Curiosity APXS. I suppose you could ask him if they checked. They probably are doing random samples of everything, and might be able to estimate elemental abundances, including gold, in Martian soils and rocks. I don’t think they got close to ice or water yet.
The APXS instrument: Canada’s contribution to Curiosity (no links to data, no real links to anything) https://www.asc-csa.gc.ca/eng/astronomy/mars/apxs.asp
There are some people using the data and applying similar methods to earth classification and mapping of resources.
K-Means Clustering of Mars Rovers APXS Oxide and Element Abundance Data and Mapping of Classified Targets in Google Earth by
Christine M. Rodrigue She teaches/taught “Geography of Mars” She points to the Planetary Data System but that link is broken. Such is the poor state of the Internet. Expect things won’t work or take forever to find. http://web.csulb.edu/~rodrigue/mars/apxs/GE/
I found the Planetary Data System, but find it obscure and sparely populated. No global search. But try this:
site:pds.nasa.gov “curiosity” “apxs” to locate things on PDS.NASA.gov
PDS Geosciences Node, Washington University in St Louis, Mars Science Laboratory (MSL) rover, Curiosity https://pds-geosciences.wustl.edu/missions/msl/
APXS Data Sets and tools at https://pds-geosciences.wustl.edu/missions/msl/apxs.htm
Instrument description https://pds-geosciences.wustl.edu/msl/msl-m-apxs-2-edr-v1/mslapx_0xxx/catalog/apxs_inst.cat
They do not mention gold, AU, but they do mention Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Zn, Br, Ge, Ga, Pb, Rb. Heavier elements (“higher Z”) can be detected in the upper 50 microns of the sample surface. So they look a bit into the material, not deep. If that were gold metal, it would be pretty obvious. You could ask them if it is fools gold (they did detect zinc and sulfur). AU is element 79 and they detected Pb (lead) at atomic number 82, so if gold were there it would be detected. It is a little instrument and takes hours to gather data. They have only had time for about a 1000 samples I think. If I were going to live on Mars, my main attention would be on the oxygen content of readily available oxides that I could scoop into my Mr Fusion to melt and separate. I would want to separate oxygen (breathing) and metals (fabricating all kinds of useful things) and just glasses (for building, sealing, and selling back on earth). I would make really tiny paper weights to send back to earth in my personal shipments.
I expect these groups studying data from the rovers would check it out. Then, of course, immediately share everything with the world to benefit all humanity.
The problem being that it is nearly impossible to find anything “shared” – even if you know the ten million specialized terms, jargon and formats. Which I do, but hate having to.
I will add “elemental abundance sensors and methods” to my long list of detectors. I try to trace out every sensor or detector on the planet (now solar system), and the communities of people developing and using them. It would help (me anyway) if people knew how to document and index and curate their own materials. NASA is one of the worst. They implicitly assume the 4.8 billion people with some level of access to the Internet have days or weeks to search and find whatever they dump on the Internet. Google is not going to do it. It needs an Internet wide, solar system wide solution, but I have not found one that I can afford.
Richard Collins, Director, The Internet Foundation