I previously said the second near equatorial area besides Arabia with the elevated GRS readings was in Tharsis. But it looks like it's actually somewhat west of Tharsis in the Medusae Fossae-Elysium region:

MEDUSAE FOSSAE-ELYSIUM REGION, MARS: DEPRESSION IN THE HEND/ODYSSEY MAP OF MARS EPITHERMAL NEUTRONS
M. A. Ivanov, M. L. Litvak, I. G. Mitrofanov, W. Boynton, R. S. Saunders.
Lunar and Planetary Science XXXIV (2003)
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1105.pdf

But Shean and Head argue that elevated GRS hydrogen readings lie within the area they suggest for relict ice from former glaciers in the lobate flow deposits off the flanks of the volcanoes in Tharsis:

Microsymposium 36, MS086, 2002
COLD BASED GLACIAL ORIGIN OF THE PAVONIS MONS LOBATE DEPOSITS.
D. E. Shean1 and J.W. Head2,
1Brown University, David_Shean@Brown.edu, 2Brown University, James_Head@Brown.edu
http://www.planetary.brown.edu/planetary/documents/Micro_36/Abstracts/086_Shean_Head.pdf

It would be interesting to look for seasonal changes in the images of this region as well.

I have a theory about why the GRS hydrogen readings of Solis Lacus are quite low when prior radar and water vapor measurements suggested high amounts of water. I'll discuss it in an upcoming post.

Bob Clark