Help Shape the Future of Space Exploration

Join The Planetary Society Now  arrow.png

Join our eNewsletter for updates & action alerts

    Please leave this field empty
The Planetary Report
Reading the Rocks On the Cover: We study rocks to discover clues about a planet's geologic and climatic history. On Earth, gray hematite (center) is commonly formed in liquid water. When scientists detected gray hematite on Mars, they pondered whether it, too, formed in water—could it be evidence of a warmer, wetter past?

Gray hematite has been identified in three locations on Mars—Valles Marineris (background), Meridiani Planum (left), and Aram crater (bottom).
Background: JPL/NASA; left: NASA/JPL/Arizona State University; center: John Betts Fine Minerals; bottom: Kees Veenenbos

Volume 24, number 1
January/February 2004

Reading the Rocks

Download this issue as a PDF
(Planetary Society members only)


6 The MarsDial: A Sundial for the Red Planet: Woody Sullivan and Jim Bell channel Bill Nye's enthusiasm for sundials.

12 Mars Rocks! Deciphering Minerals on Mars: Melissa Lane tells us how we figure out what Mars is made of.


3 Members' Dialogue Galileo, Planetary Society political advocacy, and SETI@home

4 We Make it Happen! Secret messages from Mars; building sundials

20 Q&A Why can't we see gravity? Where is Mercury 10?

22 Society News Scholarships, thank yous, and the annual audit 

Facebook Twitter Email RSS AddThis


Advocate for Space!

Fifteen years ago, Society members and passionate space advocates like you helped save the Pluto mission. Now we can do the same for missions to Europa and Mars.

Join over 27,600 people who have completed their petition and consider a donation to support advocacy efforts.

Sign Our Petition

Space in Images

Pretty pictures and
awe-inspiring science.

See More

Selfies to Space!

Take flight with a selfie on LightSail™ in 2016!

Send a Selfie Now

Connect With Us

Facebook! Twitter! Google+ and more…
Continue the conversation with our online community!