Hubble and MAVEN Unravel the Mystery of Mars' Lost Water

New findings from NASA's Hubble Space Telescope and the Mars Atmosphere and Volatile Evolution (MAVEN) mission have shed light on a long-standing Martian puzzle: the disappearance of the planet's ancient water. Through decades of detailed observation and analysis, researchers are piecing together the history of water escape from the Red Planet, deepening our understanding of planetary climate and atmospheric dynamics.

The enigma of Mars' missing water has puzzled scientists ever since the planet's once-wet surface was first recognized. Geological evidence indicates that Mars had vast amounts of water billions of years ago, yet today it's a frigid desert world. The collaborative study led by John Clarke of the Center for Space Physics at Boston University, published in Science Advances, has made significant strides using combined data from both Hubble and MAVEN.

Mars' current water loss process involves the breakup of water molecules into hydrogen and oxygen atoms by sunlight. Researchers focused on the escape of hydrogen atoms and its heavier counterpart, deuterium, into space to calculate the historical depletion of Martian water. Since deuterium escapes at a slower rate, its accumulation in the atmosphere over time serves as a proxy for measuring the volume of water lost.

The integration of MAVEN's direct measurements with Hubble's extensive historical data (dating back to 1991) enabled scientists to complete an annual cycle of Mars’ atmospheric conditions over multiple Martian years. This comprehensive view revealed the dynamic nature of the Martian atmosphere. The study found that the escape rates of hydrogen and deuterium fluctuate significantly depending on Mars' proximity to the Sun, suggesting super-thermal events provide the energy required for these atoms to escape Mar’s gravity.

These super-thermal processes could be stimulated by solar wind proton collisions or sunlight-driven chemical reactions in the upper atmosphere. This shift from the slow diffusive escape model to one that accounts for rapid atmospheric changes presents a new understanding of how water has escaped Mars' grasp.

The research not only illuminates Mars’ atmospheric history but also parallels Earth and Venus, aiding scientists in the broader exploration of exoplanets. By understanding the mechanisms behind Mars' radical climate change, from a once potentially habitable world to its current harsh state, researchers can better conceptualize the life cycles of similar planets in the cosmos.

This NASA and ESA collaborative project not only continues to expand our knowledge of the universe but also serves as preparation for MAVEN's upcoming decade-long milestone at Mars in September 2024. With the Hubble Space Telescope’s over 30 years of service and MAVEN's ongoing discoveries, our comprehension of celestial bodies and their evolutionary paths remains a constantly evolving field.