Tawhaki Vallis

It is located on Io's leading hemisphere in the equatorial plains of western Media Regio at 0°30′N 72°48′W / 0.5°N 72.8°W / 0.5; -72.8[1].

[2] Due to the shallow depth and lack of brightness or color variations associated with it, Tawhaki Vallis was seen in only a single, high-spatial-resolution observation taken by Galileo during an Io encounter on November 26, 1999.

[1] Analysis of the topography of Tawhaki Vallis shows that it is likely a lava channel, eroded into the Media Regio plain by thermal erosion.

[2] This would require the lava that flowed through to be insulated from radiative and conductive cooling along the 200-km long channel.

However, the flat floor of the channel and the lack of pit crater chains nearby would also preclude the possibility that Tawhaki Vallis is a collapsed lava tube, like Hadley Rille on the Moon.

Galileo image of Tawhaki Vallis taken in November 1999. The valley runs roughly north-south on the right side of the image. North is up. Sunlight illuminates this terrain from the left.