If you listen to the news media you may be planning a purchase of lake front property on Mars. However, NASA and others involved in the search for water on Mars are WAY more reserved in what they are saying.
Long wave radar has found what may be… moisture… a mile or two below the surface. Whether it is a body of water or mud or something else has yet to be determined. The problem with knowing is from our testing on Earth. The radar returns on Mars look similar to those we find when looking at salty water deep in the Earth. But, we also know other materials return similar signals. More study will sort out what is down there. Study has narrowed the possibilities of what may be there with the probability high it is water in some amount and form.
Much of the NASA press release information is targeted at keeping Americans enthusiastic about space exploration. It is a funding thing. I think we should be funding NASA and space exploration. But, I also acknowledge the spin NASA puts in their press releases and what the media does with the news.
No one will be buying Martian lake front property, water skies, or lawn sprinklers in the foreseeable future.
If you’re referring to the southern polar lake … it’s the European Mars Express that has obtained the radar soundings. The SHARAD instrument on NASA’s MRO has been unable to confirm. This seems in part due to issues SHARAD has had in general when operating over the south polar region, and in part possibly due to the fact it isn’t designed to penetrate as deeply as the MARSIS instrument on Mars Express (SHARAD = “SHAllow RADar”).
The returns obtained from MARSIS on Mars Express are indicative of a body of water at least 2 metres in depth (any less and the return would be sufficiently weak as to fail to register), although it could be an aquifer, rather than a free body of water. The returns also indicate that the water is exceptionally salty – necessary for it to remain liquid at the temperatures no doubt present.
The presence of salt is also in keeping with the strong evidence of subsurface water indicated by the annual recurring slope lineae (RSLs) that occur on slopes on Mars – these are “wet” patches that appear seasonally, potentially as a result of an as yet unknown mechanism forcing liquid water up through porous rock.
If interested, I routinely report on Mars in my (generally) weekly Space Sunday articles, which look at a broad range of space / astronomy related goings-on.