Engineering topics
Publications and source records attributed to Johnson, T. V..
Unexpectedly warm polar temperatures further support the idea that Io is covered virtually everywhere by cooling lava flows. This implies a new heat flow component. Io's heat flow remains constrained between a lower bound of (approximately) 2.5 W m(exp -2) and an upper bound of (approximately) 13 W m(exp -2). Additional information is contained in the original extended abstract.
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Several independent geological and geophysical investigations suggest that Europa and Ganymede contain subsurface oceans. Using Jupiter's rotating magnetic field as a primary signal, the magnetometer experiment onboard Galileo has measured secondary induction signals emanating from Europa, Ganymede, and surprisingly Callisto. The strong electromagnetic induction from these moons suggests that large global electrical conductors are located just below their icy crusts. A detailed analysis reveals that global salty oceans with salinity similar to the Earth's ocean and thicknesses in the range of approx. 6-100 kms can explain the induction observed by the Galileo magnetometer. Additional information is contained in the original extended abstract.
Assuming Io is completely resurfaced with volcanics, ages to surface units on Io can be assigned as a function of temperature. Additional information is contained in the original extended abstract.
The Europa Orbiter mission is planned as the next stage of Europa exploration. Its primary goals are to search for definitive evidence of a subsurface ocean, to characterize the ice crust and ice/water interface, and to prepare for future surface/sub-surface missions. Additional information is contained in the original extended abstract.
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Should events such as the Tvashar fire fountain be expected? Examination of the Galileo Near Infrared Mapping Spectrometer (NIMS) C3 data set shows that the chances of observing some level of active volcanism in any given area covering at least 135 km(exp 2) is quite reasonable.
Galileo has returned new high-resolution images of Io. Here we provide an overview of the encounters and science results.