Explanation: What could have formed these unusual channels? Inside Newton Basin on Mars, numerous narrow channels run from the top down to the floor. The above picture covers a region spanning about 1500 meters across. These and other gullies have been found on Mars in recent high-resolution pictures taken by the orbiting Mars Global Surveyor robot spacecraft. Similar channels on Earth are formed by flowing water, but on Mars the temperature is normally too cold and the atmosphere too thin to sustain liquid water. Nevertheless, many scientists hypothesize that liquid groundwater can sometimes surface on Mars, erode gullies and channels, and pool at the bottom before freezing and evaporating. If so, life-sustaining ice and water might exist even today below the Martian surface -- water that could potentially support a human mission to Mars. Research into this exciting possibility is sure to continue!

Here is a table of planetary comparisons. Terms which may be unfamiliar to the layperson are linked to a glossary.

Planetary Fact Sheet - U.S. Units

	MERCURY	VENUS	EARTH	MOON	MARS	JUPITER	SATURN	URANUS	NEPTUNE	PLUTO
Mass (10²¹tons)	0.364	5.37	6.58	0.081	0.708	2093	627	95.7	113	0.0138
Diameter (miles)	3032	7521	7926	2159	4222	88,846	74,897	31,763	30,775	1485
Density (lbs/ft³)	339	327	344	209	246	83	43	79	102	110
Gravity (ft/s²)	12.1	29.1	32.1	5.3	12.1	75.9	29.4	28.5	36.0	1.9
Escape Velocity (miles/s)	2.7	6.4	7.0	1.5	3.1	37.0	22.1	13.2	14.6	0.7
Rotation Period (hours)	1407.6	-5832.5	23.9	655.7	24.6	9.9	10.7	-17.2	16.1	-153.3
Length of Day (hours)	4222.6	2802.0	24.0	708.7	24.7	9.9	10.7	17.2	16.1	153.3
Distance from Sun (10⁶ miles)	36.0	67.2	93.0	0.239*	141.6	483.8	890.8	1784.8	2793.1	3647.2
Perihelion (10⁶ miles)	28.6	66.8	91.4	0.226*	128.4	460.1	840.4	1703.4	2761.6	2755.8
Aphelion (10⁶ miles)	43.4	67.7	94.5	0.252*	154.9	507.4	941.1	1866.4	2824.5	4538.7
Orbital Period (days)	88.0	224.7	365.2	27.3	687.0	4331	10,747	30,589	59,800	90,588
Orbital Velocity (miles/s)	29.7	21.8	18.5	0.64	15.0	8.1	6.0	4.2	3.4	2.9
Orbital Inclination (degrees)	7.0	3.4	0.0	5.1	1.9	1.3	2.5	0.8	1.8	17.2
Orbital Eccentricity	0.205	0.007	0.017	0.055	0.094	0.049	0.057	0.046	0.011	0.244
Axial Tilt (degrees)	0.01	177.4	23.5	6.7	25.2	3.1	26.7	97.8	28.3	122.5
Mean Temperature (F)	333	867	59	-4	-85	-166	-220	-320	-330	-375
Surface Pressure (atmospheres)	0	91	1	0	0.01	Unknown*	Unknown*	Unknown*	Unknown*	0
Number of Moons	0	0	1	0	2	39	30	21*	8	1
Ring System?	No	No	No	No	No	Yes	Yes	Yes	Yes	No
Global Magnetic Field?	Yes	No	Yes	No	No	Yes	Yes	Yes	Yes	Unknown
	MERCURY	VENUS	EARTH	MOON	MARS	JUPITER	SATURN	URANUS	NEPTUNE	PLUTO

* - See the Fact Sheet Notes

life-sustaining ice and water might exist even today below the Martian surface -- water that could potentially support a human mission to Mars.

Mission to Mars? A mission?

There is water on Mars, lots of water. When we go to Mars let's go to stay, a settlement, permanent. Enough of this Apollo thinking: a one-off design--it's the least efficient way to accomplish something lasting.

Well, of course. Apollo was a "flags and footprints" mission; good for photo-ops and our national ego, not so good for actual science or R&D.

We need to do some aggressive work in the quest for Moon bases and the (manned) exploration of Mars; either we accept the inevitable losses or we sit back and watch the Chinese. They won't let accidents stop their space program (of course they hold human life cheap but the results are what I'm referring to).

Yes, there will be losses. There were losses all along the Oregon Trail. Maybe some things are riskier than others, but you're going to go sooner or later whether it is on the way to Mars or sitting on the couch with a clicker in your hand, you know what I mean. Astronauts know this and accept it. Maybe their family and friends don't accept it as well, maybe their puppy dog tries to keep them from leaving the house every day. We're going to go into space anyway.

Americans, especially, understand the migration thing. Migration didn't stop just because the Federal Mining Law of 1876 was passed by Congress.

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Astronomy Picture of the Day

Planetary Fact Sheet - U.S. Units