Why did mars lose its atmosphere
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Why Did Mars Lose Its Atmosphere?
Introduction to Mars' Atmospheric Loss
Mars, once a planet with a thicker atmosphere capable of supporting liquid water, has undergone significant atmospheric loss over billions of years. This transformation has left Mars with a thin, cold, and dry atmosphere primarily composed of carbon dioxide. Understanding the mechanisms behind this atmospheric loss is crucial for comprehending Mars' climatic and geological evolution.
Role of Solar Wind and Sputtering
One of the primary mechanisms responsible for the loss of Mars' atmosphere is sputtering, driven by the solar wind. Mars lacks a strong intrinsic magnetic field, which means its atmosphere is directly exposed to the solar wind. Energetic particles from the solar wind collide with atmospheric molecules, ejecting them into space. This process has been significant over Mars' history, especially during periods of intense solar activity in the early solar system1 3 9.
Impact of Solar Events
Solar events, such as coronal mass ejections (CMEs), have also played a crucial role in atmospheric loss. Observations from the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft have shown that these events can enhance the escape rate of ions from Mars' atmosphere. During such events, the interaction between the solar wind and Mars' atmosphere intensifies, leading to increased atmospheric erosion6.
Isotopic Evidence and Atmospheric Composition
Measurements of isotopic ratios, particularly argon isotopes, provide evidence for the extent of atmospheric loss. Lighter isotopes are more easily ejected into space, and studies have shown that about 66% of Mars' atmosphere has been lost since the planet's formation. This isotopic fractionation indicates significant atmospheric escape over time, contributing to the transition from a warmer, wetter climate to the current cold and dry conditions1 4.
Hydrogen and Oxygen Escape
The escape of hydrogen and oxygen atoms from the upper atmosphere has also been a major factor in Mars' atmospheric loss. High-altitude water vapor, detected by the Mars Express spacecraft, can enhance the escape rate of hydrogen. This process leads to a seasonal imbalance in the escape rates of hydrogen and oxygen, further depleting the atmosphere and influencing its chemical composition over millions of years8.
Impact Erosion
Meteorite impacts have contributed to atmospheric loss by causing direct erosion and delivering volatiles to the planet. During the era of heavy bombardment, impacts would have been frequent and intense, leading to significant atmospheric erosion. However, impacts alone cannot account for the total atmospheric loss observed, suggesting that other processes, such as sputtering and solar wind interactions, have played more dominant roles5 9.
Conclusion
Mars' atmospheric loss is a complex process influenced by multiple factors, including solar wind-induced sputtering, solar events, isotopic fractionation, and meteorite impacts. These mechanisms have collectively transformed Mars from a planet with a thicker, warmer atmosphere to the cold, dry world we observe today. Understanding these processes not only sheds light on Mars' past but also informs our knowledge of atmospheric evolution on other planets, including Earth.
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Mars’ atmospheric history derived from upper-atmosphere measurements of 38Ar/36Ar
66% of Mars' atmosphere has been lost to space, contributing to the planet's climate transition from a warm, wet past to a cold, dry present.
Highly CitedLoss of the Martian atmosphere to space: Present-day loss rates determined from MAVEN observations and integrated loss through time
Loss of gas to space has been the dominant process responsible for changing Mars' climate from an early, warmer environment to the cold, dry one we see today.
Highly CitedThe Loss of Atmosphere from Mars
Yung (4) used a new method to calculate the atmospheric loss from Mars, using the sputtering process to estimate the CO2 loss.
Impact erosion of the primordial atmosphere of Mars
Impact erosion may account for an early episode of atmosphere loss from Mars, suggesting a primordial atmospheric pressure of 1 bar.
Highly CitedMAVEN observations of the response of Mars to an interplanetary coronal mass ejection
Ion loss during solar events early in Mars history may have contributed to the long-term evolution of the Mars atmosphere, as observed by MAVEN during an interplanetary coronal mass ejection impact in 2015.
Highly CitedOn Mars's Atmospheric Sputtering After MAVEN's First Martian Year of Measurements
Mars's atmospheric sputtering may contribute to atmospheric escape, but its dayside signatures are difficult to identify and its nightside impact is less significant than expected.
Elevated atmospheric escape of atomic hydrogen from Mars induced by high-altitude water
High-altitude water on Mars can significantly increase the atmospheric escape of atomic hydrogen, potentially controlling the planet's atmospheric chemistry and affecting the planet's habitability for millions of years.
Highly CitedEffects of meteorite impacts on the atmospheric evolution of Mars.
Meteorite impacts alone cannot explain the loss of significant atmospheric mass on Mars since the Late Noachian period, as other factors of atmospheric erosion and replenishment must be considered.
Loss of atmosphere from Mars due to solar wind-induced sputtering
Mars has lost approximately 3 bars of carbon dioxide due to solar wind-induced sputtering, significantly impacting our understanding of the planet's evolution.
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