![]() On this basis, comprehensive observations of hydrogen and oxygen in Mars’ upper atmosphere, and dust and water vapor in Mars’ lower atmosphere are needed. ![]() This implies that some complexities exist when dust storms expand from the lower to the upper atmosphere. This is of interest because oxygen atoms, which are mainly produced by CO 2 photodissociation in the upper atmosphere, may be affected by the change in the vertical water distribution during major dust storms. Recent studies have reported that the amount of oxygen atoms likely decreases during global/regional dust storms 14, 15, 16. Because major regional dust storms occur seasonally and global dust storms occasionally on Mars, monitoring Mars’ hydrogen upper atmosphere and dust storms is crucial for understanding its water escape mechanisms. Additionally, recent observations revealed that major dust storms, which expand regionally or globally on Mars, directly transfer water vapor from the lower to the upper atmosphere and rapidly change the vertical water distribution, increasing hydrogen escape 5, 6, 7, 8, 9, 10, 11, 12, 13. However, many observations have demonstrated that hydrogen escape rates from the Martian upper atmosphere vary seasonally due to seasonal change in vertical water vapor distribution 3, 4, 5, 6, 7. As the time scale of H 2 diffusion is 1200 years 2, it was believed that Mars’ hydrogen escape rates have been steady within a shorter time scale. A classic Martian water loss mechanism is that H 2 molecules that are chemically produced from water vapor in the lower atmosphere diffuse into the upper atmosphere, and their subsequent dissociation results in hydrogen escape 1. It is believed that, over billions of years, Mars has lost water through atmospheric escape. These findings provide insights regarding Mars’ water loss history and its redox state, which are crucial for understanding the Martian habitable environment. If dust- and wave-driven couplings of the Martian lower and upper atmospheres are common in dust storms, with increasing escape of hydrogen, oxygen will less efficiently escape from the upper atmosphere, leading to a more oxidized atmosphere. Additionally, atmospheric waves modulate dust and water transportations, causing alternate oscillations of hydrogen and oxygen abundances in the upper atmosphere. ![]() Here, we use multi-spacecraft and space telescope observations obtained during a major dust storm in Mars Year 33 to show that hydrogen abundance in the upper atmosphere gradually increases because of water supply above an altitude of 60 km, while oxygen abundance temporarily decreases via water ice absorption, catalytic loss, or downward transportation. However, it remains unclear how water is diurnally transported during a dust storm and how its elements, hydrogen and oxygen, are subsequently influenced in the upper atmosphere. Dust storms on Mars play a role in transporting water from its lower to upper atmosphere, seasonally enhancing hydrogen escape. ![]()
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