Mars liquid water stability from PNAS
This paper published in PNAS shows charts were liquid water would be stable from time to time:
Use of spacecraft data to derive regions on Mars where liquid water would be stable. From: Proc. Natl. Acad. Sci. USA, Vol. 98, Issue 5, 2132-2137, February 27, 2001
http://www.pnas.org/cgi/content/full/98/5/2132
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