Evidence of liquid water in Mars' distant past suggests that it had a substantial atmosphere compared to what it has presently. What happened to its water vapor?
A) The carbon dioxide in its atmosphere dissolved in the water and combined with surface rocks.
B) Its atmosphere was mostly hydrogen and helium. Mars' gravity is too weak to hold them.
C) The water vapor has frozen out into the polar ice caps and permafrost as Mars has cooled.
D) Mars initially had such a large greenhouse effect that the atmosphere became quite hot and slowly escaped.
E) It has now all been lost in space, including the carbon dioxide and water vapor.
C
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Why are the star clusters in tidal tails blue?
A) They are sad at being left behind. B) The individual stars were red before the interaction, and an injection of new matter onto them turned them blue. C) Blue stars are less massive and are therefore pulled away by tidal forces more easily. D) Blue stars are more massive and therefore have greater inertia, so they stay in place while the rest of the galaxy keeps moving. E) Blue stars in these newly active star-forming regions far outshine the less massive red stars.
The ____ Moon is visible above the western horizon a couple of hours before sunrise
a. waning gibbous b. waxing gibbous c. waxing crescent d. waning crescent e. new
While the orbits of planets are nearly circular, the eccentricities of the orbits of ________ are near one
Fill in the blank(s) with correct word
Which type of reaction is 2Cu(NO3)2? 2CuO + 4NO2 + O2?
a. Single-replacement b. Double-replacement c. Combination d. Decomposition