Constraining the date of the Martian dynamo shutdown by means of crater magnetization signatures
I have used a model of the Martian crustal magnetic field to constrain the timing of the Martian dynamo shut down by looking at the magnetic signatures over its craters. Our results show that the dynamo shut off after the impacts that created the Acidalia and SE Elysium basins and before the crust within the Utopia basin cooled below its magnetic blocking temperature. Accounting for the age uncertainties in the dating of these craters, we estimate that the dynamo shut off at an N(300) crater retention age of 2.5–3.2 or an absolute model age of 4.12–4.14 Ga. Moreover, we show that the Martian dynamo may have been weaker in its early stage, which if true implies that the driving mechanism of the Martian dynamo was not the same throughout its history.
A new method for inferring paleopoles using spacecraft magnetic field measurements
A magnetization distribution that has been generated by a dipole located at the center of a planetary body carries the information of the location of the poles of that dipole and this location is known as the paleopole position. Under the simplified assumption that the planetary rocks have been magnetized by a central dipole, converting the magnetization direction into paleopole locations helps us track the rotational motion of this imaginary dipole. This in turn can inform us about the presence of a planetary dynamo and its evolution in time. While paleopole positions can be estimated accurately from magnetized samples, obtaining paleopole positions based on spacecraft data requires solving a non-unique inverse problem: inverting the magnetic field measurements for the magnetization direction. Several techniques have been proposed to tackle this issue but none of them has allowed for concordant paleopole estimates among different studies until now. I have been working on a new methodology to infer paleopoles based on spacecraft data. Here you can take a look at my AGU poster with preliminary results from synthetic tests. The ultimate goal of this study is to apply the technique on planetary bodies like Mars.
This study received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 844252.