What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure?
A) We think it for purely theoretical reasons, based on calculations showing that the Sun has brightened with time.
B) The atmosphere is too cold and thin for abundant liquid water today, yet we see evidence of large areas of flowing water in the past.
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 tells us that Mars must once have been much warmer.
B
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The theory of dark energy tells us that
A) empty space is seething with a form of energy. B) there is a force that behaves like an anti-gravity. C) there is still much to learn about this universe. D) All of the above.
What is the radius of curvature of the path of a 3.0-keV proton in a perpendicular magnetic field of magnitude 0.80 T?
a. 9.9 mm b. 1.1 cm c. 1.3 cm d. 1.4 cm e. 7.6 mm
What element is behaves as the oxidizing agent in the following equation and what element behaves as the reducing agent?
Sn2+ 2 Ag ? Sn + 2 Ag? A) The tin ion, Sn2, is the oxidizing agent while silver, Ag, is the reducing agent. B) The tin ion, Sn2+, is the reducing agent while silver, Ag, is the oxidizing agent. C) The tin, Sn, is the reducing agent while silver ion, Ag?, is the oxidizing agent. D) The tin, Sn, is the oxidizing agent while silver ion,Ag?, is the reducing agent.
Which of the following did Alfred Wegener not use to support his theory of continental drift?
A) paleoclimate data B) similar fossils on widely separated continents C) paleomagnetic data D) similar rocks on widely separated continents