Mars - a planet in magnetic transition?

Planet Mars is currently an object of increasing scientific and public inte rest. Several spacecraft are on their way or planned to be sent to our neig hbour planet to unravel its secrets. One of the most unknown properties of planet Mars is whether it possesses a planetary magnetic field of dynamo or igin. Observed weak surface magnetic herds seem to argue against a currentl y operating planetary dynamo. However, weak surface fields are also expecte d if a polarity reversal occurs. We shall discuss arguments in favour and a gainst the speculation that Mars still operates an active dynamo with the w eak surface magnetic fields pointing towards an ongoing reversal. As the po ssible way to validate this speculation we discuss the importance of a sphe rical harmonic expansion of the Martian magnetic field. The planned NetLand er project and its anticipated magnetic field measurements are a powerful t ool to provide at least a low-order spherical harmonic expansion coefficien t determination of the Martian magnetic field, thereby allowing to study ch aracteristics of crustal magnetic field anomalies as well as giving clues t o the question whether Mars is a planet in magnetic transition. (C) 2000 El sevier Science Ltd. All rights reserved.