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Ancient ocean on Mars supported by global distribution of deltas and valleys

Hynek, Brian M.; di Achille, Gaetano

The climate of early Mars could have supported a complex hydrological system and possibly a northern hemispheric ocean covering up to one-third of the planet's surface. This notion has been repeatedly proposed and challenged over the past two decades, and remains one of the largest uncertainties in Mars research. Here, we used global databases of …

The role of episodic overturn in generating the surface geology and heat flow on Enceladus

Nimmo, Francis; O'Neill, Craig

The Saturnian satellite Enceladus is enigmatic in that its geologically active south polar region shows high heat flows and geysers not seen elsewhere on the satellite at present; its heavily deformed surface shows an episodic age distribution; and the current observed heat loss exceeds the long-term tidal equilibrium heat production by a factor o…

Photolysis of sulphuric acid as the source of sulphur oxides in the mesosphere of Venus

Montmessin, Franck; Bertaux, Jean-Loup; Zhang, Xi +3 more

The sulphur cycle plays fundamental roles in the chemistry and climate of Venus. Thermodynamic equilibrium chemistry at the surface of Venus favours the production of carbonyl sulphide and to a lesser extent sulphur dioxide. These gases are transported to the middle atmosphere by the Hadley circulation cell. Above the cloud top, a sulphur oxidatio…

Planetary science: Tectonic overturn on Enceladus

Helfenstein, Paul

The south pole of Saturn's icy moon Enceladus is anomalously warm, geologically youthful and cryovolcanically active. Episodic convective overturn explains how the moon's modest sources of internal heat can be channelled into intense geological activity.

Multiple origins of linear dunes on Earth and Titan

Rubin, David M.; Hesp, Patrick A.