That isn't an Ingersoll quote but a reporters comment.

if you follow the more technical link

And read the caption of figure 4, you will see that you are not just wrong, but dammned wrong.

Fig. 4. Example of Swiss-cheese observed by THEMIS in the top panel (I01162002) near the cap center at 86.5o S, 75o W, Ls 345o. The temperature ranges from ~150 (blue) to ~160 Kelvin (red).

Now 160 K is about a dozen K ABOVE the nominal thaw point of pure CO2 ice (~147 K), but it is 90 K BELOW the Eutectic (lowest possible melting point) of even the most potent brine.

Now, technically, 90 is 7.5 dozens, so the reporter's comment is broadly correct, but it's misleading.

Even with a geotherm typical of poorly conductive areas on Earth (30 K/km), you would need to go down 3 km before melting. In fact, the likely geotherm in polar regions of Mars is about 1/10 of this value, so you are talking 20-30 km depth to any liquid water.

That's basement, mate, not near-surface.

Check your facts, read the full info, and don't leap to wild guesses.