Our Earth and Its Fellow Planets [ 389 



even resembles channels. Some scientists believe they are volcanic 

 cracks; others say they are watercourses; still others hold they are 

 formed by vegetation. 



Life on Mars: Today the idea that there is human life on Mars 

 is generally discredited but we are fairly sure that plant life, at 

 least, does exist there. An analysis of the planet's atmosphere 

 reveals similarities to our own including free oxygen. This indi- 

 cates that plant life is possible, and looking through a telescope 

 we see greenish markings (probably caused by vegetation) that 

 appear to move across the face of Mars. 



The motion that we see is due to the fact that Mars is turning 

 on its axis just as the earth does. And because the axis of Mars 

 is tilted just about as much as ours, we conclude that Mars must 

 have seasons like our own. But it takes Mars nearly two years to 

 complete a journey around the sun; its seasons are therefore much 

 longer than ours, and its "year" is nearly twice as long as one of 

 our years. 



MARS WITHOUT A TELESCOPE 



When you look at the sky unaided by a telescope, Mars 

 appears reddish in contrast to the blue of other planets and stars. 

 It was this reddish tinge that led the ancients to associate the 

 planet with their god of war. Sometimes Mars is brilliant, at other 

 times dim. The variation is caused by its changing distance from 

 the earth and by its distance from the sun; Mars shines by reflected 

 sunlight. 



Sometimes Mars is 250 million miles away from the earth, and 

 sometimes as close as thirty-six million miles. When the earth is 

 between Mars and the sun, Mars is at its brightest as viewed from 

 the earth. When Mars is on the opposite side of the sun from us, 

 Mars is very dim. 



MARTIAN INVASION 



Many years ago H. G. Wells wrote a work called The War 

 of the Worlds, in which he described with great imaginative skill 

 a Martian invasion of our planet. When a dramatized version of 



