• A cold baren desert…
• … with some leftover water?
Image courtesy: NASA.
Image courtesy: Kevin Gill.
• The difference: the atmosphere!
Mars’s atmosphere today. Image courtesy: NASA.
Earth’s atmosphere today. Image courtesy: http://thebarometer.podbean.com/.
Attention: The images are not to scale!
• A complex magnetic topology
Whether we look at the radial component of the magnetic field or at the number of magnetic field lines, we conclude that Mars has a complex magnetic topology!
Radial magnetic field (Br) computed at 200 km altitude in color, overlain on gray-shaded topographic gradient map of Mars (MOLA data). The dark grey bands show regions of inadequate data coverage (Purucker et al., 2000, Plate 1).
The percent occurrence of open magnetic field lines (i.e., connecting the IMF to the Martian atmosphere) at ∼400 km altitude on the nightside and dayside (Brain et al., 2007).
• A simple approach
To understand what happened to Mars atmosphere, one approach is to focus on the electromagnetic dynamics of the atmosphere and decompose the complex magnetic field into chewable bites (Riousset et al. 2014).
Image courtesy: NASA/JPL.
This is what we did for a magnetic cusp using a dipole…
Results for a magnetic cusp created by a single dipole with moment μ=1016 A⋅m2 placed 20 km below the Martian surface. Magnetic field lines (solid magenta lines), and magnitude (color map) and direction (solid black arrows) of the current density J in the planes y=0 km and z=112 km. The dynamo current is confined in the altitude range 110≲z≲150 km.
… and for magnetic arcades using series of the same dipole.
Results for “magnetic arcades” created by nine dipoles with the same magnetic magnitudes as above. The dipoles are placed in three rows with alternating up/down directions. The six upward directed dipoles are placed at the coordinates (in kilometers) (−100; −250; −20), (0; −250; −20), (+100; −250; −20), and (−100; +250; −20), (0; +250; −20), (+100; +250; −20); the three downward directed dipoles are inserted in-between at (−100; 0; −20), (0; 0; −20), and (+100; 0; −20). Magnetic field lines (solid magenta lines), and magnitude (color map) and direction (solid black arrows) of the current density J in the planes y=0 km and z=112 km. Again, the dynamo current is confined in the altitude range 110≲z≲150 km.
• On Earth
• On Earth and Mars
Mars’ aurora? Image courtesy: ESA/Mats Holmström. The expected difference with Earth’s aurora is due to the intricate configuration of the Martian magnetic field.
Aurora Australis as captured by NASAs IMAGE satellite, overlaid onto NASAs satellite-based Blue Marble image. Image courtesy:NASA.
• Let the journey continue!
Last updated: Thursday, April 10, 2014