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PS COLUMN ARCHIVE

September 30, 2009

Ice found in newly made craters on Mars

One week ago on September 24, 2009, science team of Mars Reconnaissance Orbiter (MRO) announced the news that they discovered the ice broken loose out of newly built craters on Mars.

http://www.nasa.gov/mission_pages/MRO/news/mro-20090924r.html

On this website are illustrated in parallel two images taken by the terrain camera of MRO on October 18, 2008 and January 14, 2009 respectively. On the image taken on Oct. 18 appears a crater of about ten meters in diameter, on whose edge is clearly seen somewhat white substance like ice. On the other hand, on the image taken of the same crater on Jan. 14 disappears large portion of the white substance that surrounded the crater before, which means that the ices dispersed out of the crater sublimed to have vanished.

Although it is well known that the ice exists in Polar Regions of Mars, it is the first time to have been confirmed of its existence in underground at mid-latitude of Mars. MRO scientists say that it might be the evidence of the existence of water having formed oceans and lakes at the time of Martian mild climate.

The news itself is a very interesting discovery, however, what interested me even more is the discovery of new craters by the camera of MRO. The cameras of Mars explorers had not captured such craters at least before the time above-mentioned; therefore it proves the fact that the craters were newly made within a year or two. Moreover, they say such young craters (such a newly made crater is called “fresh crater” in English) were found in the number of more than one hundred over the area as large as the state of California. The craters are said to vary in size from two to ten meters in diameter and fifty centimeters to two and half meters in depth.

Just within one year, craters as many as one hundred have been created on Mars. They are all small craters, so Martian surface doesn’t seem to change as viewed from earth, but the proverb says, “Many small make a great”. Those fresh craters in the area size of California have broken up the Martian ground of which total area counts to 100 square meters within this one year. As total area of California is 400 square kilometers, the above fact means that entire Mars will be broken up of its ground in four million years. Four million years seems to be a long time, however, it’s only a short period of time in total Martian history.

In another word, as Martian surface was entirely broken up due to crater impacts in four million years, the ices that once existed on the surface must have been dispersed on the ground to have disappeared through sublimation phenomenon. If so assumed as above, the newly found ices from several centimeters under the ground must have seeped out to the surface from deeper level, deep enough not to have been affected by crater impacts, and finally ended up being trapped on the Martian surface.

At any rate, my opinion is that mysteries of Martian water will not be clarified after all, unless underground structures of Mars are more clearly revealed. Only with the information of the underground structures, water cycle of Mars will be unraveled, from where will proceed to revealability of history of Martian lives.

At this time, however, NASA has no plan of exploring Martian underground structures. I sincerely hope that the day will come when Japanese exploration of Mars will pay keen attention to the underground conditions of Mars where lies the most important clue for clarifying Martian history from scientific viewpoint.

Please send your comments, if any, to pscolumn@planetary.or.jp

(Translated by The Planetary Society of Japan)