What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure?
A) The atmosphere is too cold and thin for liquid water today, yet we see evidence of flowing water in the past.
B) We think it for purely theoretical reasons, based on calculations showing that the Sun has brightened with time.
C) The presence of inactive volcanoes on Mars tells us that there must once have been a lot of outgassing, and hence a thicker atmosphere.
D) The fact that parts of Mars have a lot of craters tell us that Mars must once have been much warmer.
A) The atmosphere is too cold and thin for liquid water today, yet we see evidence of flowing water in the past.
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Two blocks in contact with each other are pushed to the right across a rough horizontal surface by the two forces shown. If the coefficient of kinetic friction between each of the blocks and the surface is 0.30, determine the magnitude of the force exerted on the 2.0-kg block by the 3.0-kg block
a.
15 N
b.
25 N
c.
11 N
d.
22 N
e.
33 N
Simple Harmonic Motion: If a floating log is seen to bob up and down 15 times in 1.0 min as waves pass by you, what are the frequency and period of the wave?
Fill in the blank(s) with the appropriate word(s).
Neptune has a methane-rich atmosphere
a. True b. False Indicate whether the statement is true or false
The explosion of a supernova type II can leave behind
a. a planetary nebula. b. a shell of hot, expanding gas with a white dwarf at the center. c. a shell of hot, expanding gas with a neutron star at the center. d. Nothing is ever left behind.