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Register a new userThe surface age of Sputnik Planum, Pluto, must be less than 10 million years
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Authors
David E. Trilling
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Data from the New Horizons mission to Pluto show no craters on Sputnik Planum down to the detection limit (2 km for low resolution data, 625 m for high resolution data). The number of small Kuiper Belt Objects that should be impacting Pluto is known to some degree from various astronomical surveys. We combine these geological and telescopic observations to make an order of magnitude estimate that the surface age of Sputnik Planum must be less than 10 million years. This maximum surface age is surprisingly young and implies that this area of Pluto must be undergoing active resurfacing, presumably through some cryo-geophysical process. We discuss three possible resurfacing mechanisms and the implications of each one for Plutos physical properties.
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The deep nitrogen-covered Sputnik Planitia (SP; informal name) basin on Pluto is located very close to the longitude of Plutos tidal axis[1] and may be an impact feature [2], by analogy with other large basins in the solar system[3,4]. Reorientation[5-7] due to tidal and rotational torques can explain SPs location, but requires it to be a positive gravity anomaly[7], despite its negative topography. Here we argue that if SP formed via impact and if Pluto possesses a subsurface ocean, a positive gravity anomaly would naturally result because of shell thinning and ocean uplift, followed by later modest N2 deposition. Without a subsurface ocean a positive gravity anomaly requires an implausibly thick N2 layer (greater than 40 km). A rigid, conductive ice shell is required to prolong such an oceans lifetime to the present day[8] and maintain ocean uplift. Because N2 deposition is latitude-dependent[9], nitrogen loading and reorientation may have exhibited complex feedbacks[7].
Annular structures, or rings and gaps, in disks around pre-main sequence stars have been detected in abundance towards Class II objects ~1,000,000 years in age. These structures are often interpreted as evidence of planet formation, with planet-mass bodies carving rings and gaps in the disk. This implies that planet formation may already be underway in even younger disks in the Class I phase, when the protostar is still embedded in a larger scale dense envelope of gas and dust. While younger disks likely play an important role in the onset of planet formation, only within the past decade have detailed properties of disks in the youngest star-forming phases begun to be observed. Here we present 1.3 mm dust emission observations with 5 au resolution that show four annular substructures in the disk of the young (<500,000 years) protostar IRS 63. IRS 63, a single Class I source located in the nearby Ophiuchus molecular cloud (at a distance of 144 pc), is one of the brightest Class I protostars at (sub)millimeter wavelengths that also has a relatively large disk (>50 au). Multiple annular substructures observed towards disks at young times can act as an early foothold for dust grain growth, a prerequisite of planet formation. Whether planets already exist or not in the disk of IRS 63, it is clear that the planet formation process begins in the young protostellar phases, earlier than predicted by current planet formation theories.
The Transiting Exoplanet Survey Satellite (TESS) is the first high-precision full-sky photometry survey in space. We present light curves from a magnitude limited set of stars and other stationary luminous objects from the TESS Full Frame Images, as reduced by the MIT Quick Look Pipeline (QLP). Our light curves cover the full two-year TESS Primary Mission and include $sim$ 14,770,000 and $sim$ 9,600,000 individual light curve segments in the Southern and Northern ecliptic hemispheres, respectively. We describe the photometry and detrending techniques we used to create the light curves, and compare the noise properties with theoretical expectations. All of the QLP light curves are available at MAST as a High Level Science Product via doi.org/10.17909/t9-r086-e880 (https://archive.stsci.edu/hlsp/qlp). This is the largest collection of TESS photometry available to the public to date.
Sputnik Planitia, Plutos gigantic ice glacier, hosts numerous scientific mysteries, including the presence of thousands of elongated pit structures. We examine various attributes of these pit structures in New Horizons data sets, revealing their length, aspect ratios, and orientation properties; we also study their interior reflectivities, colors, and compositions, and compare these attributes to some other relevant regions on Pluto. We then comment on origin mechanisms of the pits and also the fate of the missing volatiles represented by the pits on Sputnik Planitia.
The New Horizons spacecraft mapped colors and infrared spectra across the encounter hemispheres of Pluto and Charon. The volatile ices CH$_4$, CO, and N$_2$, that dominate Plutos surface, have complicated spatial distributions resulting from sublimation, condensation, and glacial flow acting over seasonal and geological timescales. Plutos H$_2$O ice bedrock is also mapped, with isolated outcrops occurring in a variety of settings. Plutos surface exhibits complex regional color diversity associated with its distinct provinces. Charons color pattern is simpler, dominated by neutral low latitudes and a reddish northern polar region. Charon near infrared spectra reveal highly localized areas with strong NH$_3$ absorption tied to small craters with relatively fresh-appearing impact ejecta.
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