Venus: Defying the Solar Wind Without a Magnetic Shield

Venus has no magnetic shield, yet its atmosphere remains astonishingly thick. How does a planet withstand the solar wind without a protective magnetosphere? The answer lies in the complex interaction between the solar wind and Venus’ ionosphere, which forms an induced magnetosphere that shields the atmosphere from complete erosion. Ion escape, primarily of oxygen ions, dominates present-day atmospheric loss, with measurements from Pioneer Venus Orbiter and Venus Express revealing typical escape rates of 10²⁴–10²⁵ O⁺/s. Surprisingly, despite this constant bombardment, Venus’ atmosphere remains stubbornly thick, suggesting that solar wind-driven escape alone may be insufficient to account for the loss of hypothetical ancient oceans. This raises unresolved questions about Venus’ atmospheric evolution, including how solar wind–atmosphere interactions may have differed in its early history. Studying these processes sheds light not only on Venus’ evolution but also on how rocky worlds without magnetic shields can survive harsh space weather.