PLANETARY MUSINGS

Entries in "Mercury"

Video on MESSENGER 1st flyby of Mercury

The American Museum of Natural History just released this great Science Bulletin video story highlighting the MESSENGER mission and the 1st flyby of Mercury back in January.

Iron snow on Mercury

One of the active areas of research in our group is developing understanding of mechanisms that can drive convection inside the metallic cores of solid planets and moons. Why? To understand what may be driving magnetic fields. Previously, we had demonstrated that in contrast to the Earth, Ganymede's magnetic field could be the result of solid iron precipitating at the core-mantle boundary and "snowing" inward, driving compositional convection. Based on new experimental results by colleagues Bin Chen and Jie Li at the University of Illinois we have shown that a similar set of results is possible for Mercury. The effect at Mercury is pronounced by non-ideal melting behavior of the Fe-FeS system at modest pressures. Indeed, it turns out that Mercury could also evolve to a state of having to distinct and separated zones of snowing iron in its core. All of these results will be useful in understanding the results that will be gained by the MESSENGER mission to Mercury once it gets into orbit.

Citation:
Chen, Bin, Jie Lie, and Steven A. Hauck, II, Non-ideal liquidus curve in the Fe-FeS system and Mercury's snowing core , Geophys. Res. Lett., 35, L07201, doi: 10.1029/2008GL033311 (2008). Article

Graduate Study in Earth and Planetary Science

The Department of Geological Sciences at Case Western Reserve University is currently accepting applications from students interested in pursuing graduate studies leading to M.S. and Ph.D. degrees in the earth, environmental, and planetary sciences. The Department offers flexible, research-intensive programs for graduate students. Applications are accepted on a continuing basis, though students requesting financial support are strongly encouraged to apply by February 1, 2008. Online applications are available through the School of Graduate Studies.

There are several opportunities for students interested in pursuing research in planetary science, particularly in the areas of planetary geology and geophysics, high-pressure and temperature geochemistry, and meteorites working with a group of faculty that includes myself, Prof. Harvey, and Prof. Van Orman.

At present I am collaborating with students to (1) understand the nature of Mars' crust and lithosphere and tectonic activity and (2) the mechanisms responsible for driving Ganymede's magnetic field. (3) I am also looking for graduate students interested in working with me on analyzing data from the MESSENGER Mission to Mercury to understand both the internal and tectonic evolution of that planet Additional opportunities within these may be available depending upon interest. We are also in the process of focusing new study on large lunar impact basins.

I would welcome the opportunity to discuss opportunities for graduate study in planetary science and/or geophysics with interested students (my contact info is available on my webpage).

Papers for the Lunar and Planetary Science Conference

We have two papers accepted for the upcoming 38th Lunar and Planetary Science Conference in Houston. LPSC is the primary planetary science meeting of the year. This year our group will be giving two posters on the origin and interpretation of major tectonic features on Mars and Mercury.

Ritzer, J. A., and S. A. Hauck, II (2007). Influence of external loads on interpretations of lithospheric flexure and tectonics at Isidis Planitia, Mars, Lunar and Planet. Sci., 38, 2244.pdf.

Dombard, A. J., and S. A. Hauck, II (2007). Despinning plus global contraction and the orientation of lobate scarps on Mercury, Lunar and Planet. Sci., 38, 2026.pdf.

These presentations will be made March 12-16, 2007 in League City, TX.

Opportunities for Graduate Study in Planetary Geology and Geophysics

The Department of Geological Sciences at Case Western Reserve University is currently accepting applications from students interested in pursuing graduate studies leading to M.S. and Ph.D. degrees in the earth, environmental, and planetary sciences. The Department offers flexible, research-intensive programs for graduate students. Applications are accepted on a continuing basis, though students requesting financial support are strongly encouraged to apply by February 1, 2007. Online applications are available through the School of Graduate Studies.

There are several opportunities for students interested in pursuing research in planetary science, particularly in the areas of planetary geology and geophysics, high-pressure and temperature geochemistry, and meteorites working with a group of faculty that includes myself, Prof. Harvey, and Prof. Van Orman.

At present I am collaborating with students to (1) understand the nature of Mars' crust and lithosphere and tectonic activity and (2) the mechanisms responsible for driving Ganymede's magnetic field. Additional opportunities within these may be available depending upon interest. We are also in the process of focusing new study on large lunar impact basins and the coupled internal and tectonic evolution of Mercury.

I would welcome the opportunity to discuss opportunities for graduate study in planetary science and/or geophysics with interested students (my contact info is available on my webpage).

24 million km laser link

D. E. Smith, M. T. Zuber, X. Sun, G. A. Neumann, J. F. Cavanaugh, J. F. McGarry, T. W. Zagwodzki, Two-Way Laser Link over Interplanetary Distance, Science, 311, 53, (2006), Article.

Clearly one of the coolest "simple" experiments I have seen lately.  The MESSENGER spacecraft, which is on its way to Mercury, made a two-way laser link with Earth last May.  Apparently, at approximately 24 million km (a true interplanetary distance) that is a new distance record for detecting a laser.  The link was made both by the Mercury Laser Altimeter (MLA) pointing at telescopes at NASA's Goddard Geophysical and Astronomical Observatory and simultaneous pointing of an Earth-based laser at the same location toward the spacecraft.  The experiment is useful as a calibration of the MLA instrument in space as well as establishing that such an experiment can be accomplished.  Two-way laser communication may become important for future spacecraft which need precise distance and other measurements, like the proposed LISA mission to search for gravity waves.

A thin shell dynamo at Mercury?

Stanley, S, J Bloxham, WE Hutchison, and MT Zuber, Thin shell dynamo models consistent with Mercury's weak observed magnetic field, EPSL, 234, 27-38, (2005), doi:10.1016/j.epsl.2005.02.040.

Ever since Mercury's magnetic field was discovered by Mariner 10 back in 1974-1975 its origin has been somewhat of enigma. The basic observation was that the rate of increase in strength of the magnetic field as the spacecraft got closer to the planet was consistent with an internal field with a dipolar character. The strength of the field, however, is pretty weak compared to the Earth's. One possibility is that the magnetic field is generated by a dynamo, just one that doesn't behave exactly like the ours. Stanley et al [2005] focus on the idea that the character of the dynamo and magnetic field may be a function of the relative thickness of the liquid outer core. The Earth's inner core is only about 35% of the radius of the whole core, but that isn't necessarily true for other planets.

Stanley et al., argue that based on magnetostrophic balance assumtpions that the ratio of the strength of the dipolar component of Mercury's magnetic field to the inferred toroidal component is a factor of 10-1000 less than the Earth's if a dynamo is involved. They set out to assess whether a dynamo in a thin shell (inner core is 70% or more of radius of core) could explain this phenomena. The basic result was that yes it could if the modified Rayleigh number (a modified scaling of the ratio of buoyancy to Coriolis forces in this case) was modest.

One of the conclusions that they had that isn't clear to me is how "differential rotation" (apparently the mechanism for creating the toroidal field) can drive a dynamo. Where is the differential rotation, between the inner core and the mantle? They also suggested that it may be possible for the character of the magnetic field to vary with position inside and outside the tangent cylinder (imagine a cylinder placed around the inner core along the axis of rotation). If true that might be observable by the MESSENGER spacecraft when it gets to Mercury in 2011. Though I wonder what exactly we might look for in those data...