Preface: The Mars Atmosphere and Volatile Evolution (MAVEN) Mission

Abstract

The solar system began in the early solar nebula when the gas and dust accreted to form planetesimals which accumulated into the larger bodies we now know as the planets. Mars, the fourth planet from the sun was less massive than its two neighbors, Jupiter and Earth. But it had grown large enough to differentiate, forming a core and mantle and topped by a crust. It also was surrounded by an atmosphere. This early atmosphere appears to have provided a relatively benign environment, with surficial water that was much more abundant and geologically active than is possible on Mars today. Now, the surface of Mars is cold and dry, and any liquid water will very quickly either freeze or evaporate/sublimate into the atmosphere. We want to understand how this transition in climate occurred, and what role loss of gas from the atmosphere to space played in this climate change. The records of how the atmosphere evolved are difficult to decipher. We can determine how loss processes operate today, and try to extrapolate backward in time. It is not sufficient to simply use the present day loss rate because the conditions that led to that atmospheric evolution were not the same throughout Mars’ history but changed as the Sun evolved. So we must study the loss of atmosphere as a function of solar conditions and apply what we know about the evolution of the Sun to account for these changing conditions and make an accurate estimate of the losses with time. We also can examine characteristics such as the ratios of isotopes of light stable gases and noble gases for clues to the integrated loss to space over time. A major step in being able to do this was the development of the Mars Atmosphere and Volatile Evolution (MAVEN) mission as part of NASA’s Scout program. MAVEN is led by a Principal Investigator, and involves collaboration between the University of Colorado’s Laboratory for Atmospheric and Space Physics, the University of California at Berkeley’s Space Sciences Laboratory, NASA’s Goddard Space Flight Center and Jet Propulsion Laboratory, and Lockheed Martin. While many missions have flown to Mars, none has had such