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  • Writer's pictureLeah Sacks

Spurious Summaries

For today's blog, I was asked to write summaries of journal articles. Two of the summaries will be of true journal articles, while the third will be a summary that I made up. My lab mates will then try to guess which summary is fake. The point of this exercise is to both encourage us to read articles, as well as to identify what characteristics we can use to identify true science. So, without further ado, here are my three summaries with titles. This is a useless exercise if the reader searches the titles as one will obviously be fake. So don't do that.

Vincent Le Moign, CC BY 4.0 via Wikimedia Commons

Summary of Article 1

Title: "Tidal relationships of the Pluto and Charon system and corresponding tectonic features"

Pluto and Charon, one of Pluto’s moons, are what is called “tidally locked” where the same side of Charon faces Pluto all the time and Charon’s orbit is essentially circular. It has a very low eccentricity. This means that currently, Pluto and Charon exert only basic gravitational tides on each other. In the past, Charon likely had a much more eccentric, or elliptical, orbit. Thus, in the past, the tidal bulges of both Charon and Pluto would have pulled on each other, slowly circularizing Charon’s orbit and exerting strong tidal forces. This study examines theoretical primordial, or initial, eccentricities for Charon and the resulting tidal forces on both bodies. Stress modeling indicates higher heat flow levels in equatorial areas of both bodies. Experimental results showed that higher starting eccentricities resulted in higher heat flow levels. The authors then extrapolated from tidal stress maps where topographic features that would correspond with local heat flux maximums and minimums would be located. The authors noted that these theoretical locations correlate with several observed features including rifting west of Serenity Chasma on Charon, theorized fracture fields on the southern hemisphere of Charon, which have since been resurfaced, and large canyons in Lowell Regio on Pluto. The author’s also noted the interesting location of these features and suggested that it may have implications for possible reorientation of Charon in the past.

Summary of Article 2

Title: "Implications from Ithaca Chasma for the thermal and orbital history of Tethys"

Ithaca Chasma, on Tethys, is one of a couple large chasmata systems in the outer solar system. This paper looked at profiles perpendicular to the long direction of the chasm to study flexure. Flexure, by definition, looks at the curve of the lithosphere, particularly in response to stress. This paper works from the basis that you can reconstruct what the flexure was at the time that Ithaca Chasm formed and then get an idea of the thickness of the surface portion of the crust and the heat flow at the time that the chasm was forming. From there, this paper extrapolates to gain a perspective on global heat flow. Using the calculated heat values, the study then proceeds to determine the orbital and tidal conditions that would produce the appropriate amount of heat. Tidal forces pull on a planet in multiple directions, increasing heat flow throughout the planet. By understanding possible scenarios that would produce enough heat to create the flexure observed at Ithaca Chasma, we can gain an understanding of possible “thermal and orbital histor[ies] of Tethys” as the title of the paper says. The methods of this paper outline the equations and model parameters used to determine possible histories. The authors determined that eccentricities around (~.001-.02), which is relatively close to a circular orbit, can produce around 100 GW of heat flow, which is what was determined by the flexure. The authors determined that it is necessary to asses local heat sources as opposed to simply global heat flow. They also determined that a resonance between Tethys and Dione was probably not enough heat on its own to produce the topography seen at Ithaca Chasma and periodic heating rather than equilibrium tidal heating may be necessary. Summary of Article 3

Title: "Geophysical implications of the long-wavelength topography of the Saturnian satellites"

Tethys Dione, Rhea, and Iapetus, Mimas, Enceladus, and Europa are all studied in this paper. The authors use a technique involving long-wavelength topography that looks at the variations in topography on a larger scale than in a DEM or similar. This variation in topography, which encompasses both vertical variation as well as spacing, is expressed in terms of spherical harmonics. The study maps out the observed topography at .2 km scale vertical variation and compares them and the resulting spherical harmonic calculations across all of the previously listed bodies. From the variations in topography, the authors are able to draw conclusions and calculated likely ranges for lithospheric thickness. Topography is a direct loading or unloading of the lithosphere and the shape of the lithosphere directly relates to its thickness. From their studies, the authors conclude that Mimas, Enceladus, and Tethys are likely not in hydrostatic equilibrium, meaning that their surfaces are not at rest in some way. They suggest it is likely detectable if a mission were to be sent to any of these moons. The authors do not think their observations are explainable by the influence of impact craters on these surfaces, though they do think that active processes on Enceladus explain the results from that moon. Mimas and Tethys may have some form of unexplained elastic support or structural differences that would explain the results of this study. The authors conclude by noting that they have shown that limb profiles, which were the sources for the study, can be used to create long-wavelength topography maps.

Well, there we go. We'll see how the lab meeting goes! Credit goes to the authors of the above listed articles. If I remember, I shall return and add the authors after my lab meeting.

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