New Horizons Found Evidence of Sand Dunes Made of Methane on Pluto

Scientists say they have found evidence of dunes of frozen methane on Pluto.

The research, which is published in the journal Science, suggests that the distant world is more dynamic than previously thought.

Pluto's atmosphere was believed to be too thin to create the features familiar in deserts on Earth.

The findings come from analysis of the startling images sent back by Nasa's New Horizons mission, which flew close to Pluto in July 2015.

After an epic trek through the Solar System that took nearly a decade, New Horizons sped by at a speed of 58,536 km/h (36,373 mph), gathering data as it passed.

In their study, the researchers explain how they studied pictures of a plain known as Sputnik Planitia, parts of which are covered with what look like fields of dunes.

They are lying close to a range of mountains of water ice 5km high.

The scientists conclude that the dunes are 0.4-1km apart and that they are made up of particles of methane ice between 200-300 micrometers in diameter - roughly the size of grains of sand.

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Fly Over Pluto

Video is based on data and images from New Horizons.

Pluto's Interacting Surface & Atmosphere

The Puzzling Detection of X-rays From Pluto by Chandra

The Puzzling Detection of X-rays From Pluto by Chandra

Authors:

Lisse et al

Abstract:

Using Chandra ACIS-S, we have obtained imaging Xray spectrophotometry of the Pluto system in support of the New Horizons flyby on 14 July 2015. 174 ksec of observations were obtained on 4 visits in Feb 2014 to Aug 2015. We measured a net signal of 6.8 counts and a noise level of 1.2 counts in a comoving 11 x 11 pixel box (100 x 100 R_Pluto) in the 0.31 to 0.60 keV passband for a detection at > 99.95 C.L. The Pluto photons do not match the background spectrum, are coincident with a 90% flux aperture comoving with Pluto, and are not sky source confused. The mean 0.31 to 0.60 keV Xray power from Pluto is 200 MW, in the midrange of Xray power levels seen for known solar system emission sources: auroral precipitation, solar Xray scattering, and charge exchange (CXE) between solar wind (SW) ions & atmospheric neutrals. We eliminate auroral effects as a source, as Pluto has no known magnetic field & the New Horizons Alice UV spectrometer detected no airglow from Pluto during the flyby. Nano-scale atmospheric haze particles could lead to enhanced resonant scattering of solar X-rays from Pluto, but the energy signature of the detected photons does not match the solar spectrum and estimates of Plutos scattered Xray emission are > 100 times below the 3.9e-5 cps found in our observations. CXE emission from SW carbon, nitrogen, and oxygen ions can produce the energy signature seen, and the 6e25 neutral gas escape rate from Pluto deduced from New Horizons data can support the 3.0e24 Xray photons/sec emission rate required by our observations. Using the SW proton density and speed measured by the Solar Wind Around Pluto (SWAP) instrument in the vicinity of Pluto at the time of the photon emissions, we find too few SW minor ions flowing into the 11 x 11 pixel box centered on Pluto than are needed to support the observed emission rate unless the SW is significantly focused and enhanced in this region.

Sputnik Planitia may Dominate Pluto

Icy heart could be key to Pluto’s strange geology

Author:

Witze

Abstract:

Pluto’s icy heart beats with a planetary rhythm.

When NASA’s New Horizons spacecraft whizzed by the dwarf planet in July 2015, it famously spotted a heart-shaped feature just north of the equator. Now, researchers are recognizing how that enormous ice cap drives much of Pluto’s activity, from its frosty surface to its hazy atmosphere.

Planetary scientists revealed their latest insights this week at a joint meeting of the American Astronomical Society’s Division for Planetary Sciences and the European Planetary Science Congress in Pasadena, California. Many of those discoveries revolve around Sputnik Planitia, the icy expanse that makes up the left lobe of Pluto’s ‘heart’. “All roads lead to Sputnik,” says William McKinnon, a planetary scientist at Washington University in St. Louis, Missouri.

Researchers already knew that Sputnik Planitia (formerly dubbed Sputnik Planum) is made mostly of nitrogen ice, churning and flowing in massive glaciers1. But its sheer size — 1,000 kilometres across and at least several kilometres deep — means that it exerts extraordinary influence over the dwarf planet’s behaviour.

The heart may have even knocked Pluto on its side. At the meeting, James Tuttle Keane of the University of Arizona in Tucson showed how the feature’s formation could have altered Pluto’s tilt. Sputnik Planitia may be a crater punched by a giant meteorite impact, which later filled with ice. The sheer mass of all that ice caused the dwarf planet to rotate relative to its spin axis, Keane says, so that Sputnik Planitia ended up permanently facing away from Pluto’s biggest moon, Charon. “Pluto followed its heart,” he says. (Other scientists, such as Douglas Hamilton of the University of Maryland in College Park, have suggested that Sputnik Planitia might have accumulated ice without an impact, and that the hole instead comes from the sheer weight of the ice depressing the ground beneath it.)

News From Pluto: Clouds on Pluto, Landslides on Charon

By the end of this week, all the data gathered by the New Horizons spacecraft during its July 2015 flyby of the Pluto system will have finished downloading to Earth and be in the hands of the science team. Bonnie Buratti, a science team co-investigator said they have gone from being able to look at the pretty pictures to doing the hard work required to study the data. During today’s press briefing from the Division of Planetary Sciences conference, the New Horizons team shared a few interesting and curious findings they’ve found in the data so far.

While the famous global view of Pluto appears to show a cloud-free dwarf planet, Principal investigator Alan Stern said the team has now take a closer look and found handful of potential clouds in images taken with New Horizons’ cameras.

“Clouds are common in the atmospheres of the solar system,” Stern said during the briefing, “ and a natural question was whether Pluto, with a nitrogen atmosphere, has any clouds.”

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Landing on Pluto

Charon's Argo Chasm is 185 Miles Long & Up to 5.5 Miles Deep

The Grand Canyon on Earth might feel a little inadequate if it ever learns about Argo Chasma on Pluto's moon Charon. Charon is home to a canyon 185 miles (300 kilometers) long and up to 5.5 miles (9 kilometers) deep in places. NASA says Argo Chasma also has one of the tallest known cliff faces in the entire solar system.

Scientists are working with images and data from the New Horizons spacecraft, which launched in 2006 and reached dwarf planet Pluto in 2015. Compared to the Grand Canyon in the US, Argo Chasma is five times deeper and 150 miles (240 kilometers) longer. Imagine the sheer terror of looking down if someone ever builds an Argo Chasma Skywalk with a glass floor.

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Evidence of a Subterranean Ocean on Pluto

Recent Tectonic Activity on Pluto Driven by Phase Changes in the Ice Shell

Authors:

Hammond et al

Abstract:

The New Horizons spacecraft has found evidence for geologic activity on the surface of Pluto, including extensional tectonic deformation of its water ice bedrock (see Moore et al. [2016]). One mechanism that could drive extensional tectonic activity is global surface expansion due to the partial freezing of an ocean. We use updated physical properties for Pluto and simulate its thermal evolution to understand the survival of a possible subsurface ocean. For thermal conductivities of rock less than 3 W m−1 K−1, an ocean forms and at least partially freezes, leading to recent extensional stresses in the ice shell. In scenarios where the ocean freezes and the ice shell is thicker than 260 km, ice II forms and causes global volume contractions. Since there is no evidence for recent compressional tectonic features, we argue that ice II has not formed and that Pluto's ocean has likely survived to present day.

Modeling glacial flow on and onto Pluto's Sputnik Planum

Modeling glacial flow on and onto Pluto's Sputnik Planum

Authors:

Umurhan et al

Abstract:

Observations of Pluto's surface made by the New Horizons spacecraft indicates present-day nitrogen ice glaciation in and around the basin known as Sputnik Planum. Motivated by these observations, we have developed an evolutionary glacial flow model of solid nitrogen ice taking into account its published thermophysical and rheologies properties. This model assumes that glacial ice layers flow laminarly and have low aspect ratios which permits a vertically integrated mathematical formulation. We assess the conditions for the validity of laminar nitrogen ice motion by revisiting the problem of the onset of solid-state buoyant convection of nitrogen ice for a variety of bottom thermal boundary conditions. Subject to uncertainties in nitrogen ice rheology, nitrogen ice layers are estimated to flow laminarly for thicknesses less than 400-1000 meters. The resulting mass-flux formulation for when the nitrogen ice flows as a laminar dry glacier is characterized by an Arrhenius-Glen functional form. The flow model developed is used here to qualitatively answer some questions motivated by observed glacial flow features found on Sputnik Planum. We find that the wavy transverse dark features found along the northern shoreline of Sputnik Planum may be a transitory imprint of shallow topography just beneath the ice surface suggesting the possibility that a major shoreward flow event happened relatively recently within the last few hundred years. Model results also support the interpretation that the prominent darkened features resembling flow lobes observed along the eastern shoreline of the Sputnik Planum basin may be a result of wet nitrogen glacial ice flowing into the basin from the pitted highlands of eastern Tombaugh Regio.

Detection of CO and HCN in Pluto's atmosphere with ALMA

Detection of CO and HCN in Pluto's atmosphere with ALMA

Authors:

Lellouch et al

Abstract:

Observations of the Pluto-Charon system, acquired with the ALMA interferometer on June 12-13, 2015, have yielded a detection of the CO(3-2) and HCN(4-3) rotational transitions from Pluto, providing a strong confirmation of the presence of CO, and the first observation of HCN, in Pluto's atmosphere. The CO and HCN lines probe Pluto's atmosphere up to ~450 km and ~900 km altitude, respectively. The CO detection yields (i) a much improved determination of the CO mole fraction, as 515+/-40 ppm for a 12 ubar surface pressure (ii) clear evidence for a well-marked temperature decrease (i.e., mesosphere) above the 30-50 km stratopause and a best-determined temperature of 70+/-2 K at 300 km, in agreement with recent inferences from New Horizons / Alice solar occultation data. The HCN line shape implies a high abundance of this species in the upper atmosphere, with a mole fraction >1.5x10-5 above 450 km and a value of 4x10-5 near 800 km. The large HCN abundance and the cold upper atmosphere imply supersaturation of HCN to a degree (7-8 orders of magnitude) hitherto unseen in planetary atmospheres, probably due to the slow kinetics of condensation at the low pressure and temperature conditions of Pluto's upper atmosphere. HCN is also present in the bottom ~100 km of the atmosphere, with a 10-8 - 10-7 mole fraction; this implies either HCN saturation or undersaturation there, depending on the precise stratopause temperature. The HCN column is (1.6+/-0.4)x10^14 cm-2, suggesting a surface-referred net production rate of ~2x10^7 cm-2s-1. Although HCN rotational line cooling affects Pluto's atmosphere heat budget, the amounts determined in this study are insufficient to explain the well-marked mesosphere and upper atmosphere's ~70 K temperature. We finally report an upper limit on the HC3N column density (< 2x10^13 cm-2) and on the HC15N / HC14N ratio (< 1/125).

Sputnik Planum Seems to be Undergoing Convection

On Pluto, icebergs floating in a sea of nitrogen ice are key to a possible explanation of the quilted appearance of the Sputnik Planum region of the dwarf planet's surface.

Data reported by NASA's New Horizons New Horizons mission to the Pluto system shows unusual terrain in this region, which features a large deposit of nitrogen ice with a pattern of polygons that are thickest at their centers and dip at their edges. Purdue University researchers have proposed that the polygons seen in the images could be individual Rayleigh-Bénard convection cells. A paper detailing the work will be published in the journal Nature online on Thursday (June 2).

Purdue graduate student Alex Trowbridge, under the guidance of Jay Melosh, a distinguished professor of earth, atmospheric and planetary sciences, and professor of physics and aerospace engineering, led the research.

"Evidence suggests this could be a roiling sea of volatile nitrogen ice," Melosh said. "Imagine oatmeal boiling on the stove; it doesn't produce one bubble for the entire pot as the heated oatmeal rises to the surface and the cooler oatmeal is pushed down into the depths, this happens in small sections across the pot, creating a quilted pattern on the surface similar to what we see on Pluto. Of course, on Pluto this is not a fast process; the overturn within each unit happens at a rate of maybe 2 centimeters per year."

The surface of Pluto appears to be primarily very cold water ice. However, within the Sputnik Planum region the icy surface drops into a basin that holds a pool of nitrogen ice. Both water and nitrogen are solids at Pluto's temperatures, but the nitrogen ice is structurally weak and has a low viscosity that allows it to deform and flow like a fluid, while the water ice has a very high viscosity and can form tall, hard mountains, Trowbridge said.

"Within this pool of nitrogen ice, there are mountains of water ice that have collected at the edges of the polygons," he said. "The way they have collected suggests they have moved or floated like icebergs with the convection current. If this is true, we can calculate how deep the pool would need to be for the icebergs to float freely without catching on the bottom."

The polygons also can provide information about the depth of the pool of nitrogen through known ratios of width to depth for individual cells of convection, he said.

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The Closest Close up of Pluto yet From New Horizons

Surface Compositions Across Pluto and Charon

Surface Compositions Across Pluto and Charon

Authors:

Grundy et al

Abstract:

The New Horizons spacecraft mapped colors and infrared spectra across the encounter hemispheres of Pluto and Charon. The volatile ices CH4, CO, and N2, that dominate Pluto's surface, have complicated spatial distributions resulting from sublimation, condensation, and glacial flow acting over seasonal and geological timescales. Pluto's H2O ice "bedrock" is also mapped, with isolated outcrops occurring in a variety of settings. Pluto's surface exhibits complex regional color diversity associated with its distinct provinces. Charon's 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 NH3 absorption tied to small craters with relatively fresh-appearing impact ejecta.

The Geology (Hadeology) of Pluto and Charon Through the Eyes of New Horizons

The Geology of Pluto and Charon Through the Eyes of New Horizons

Authors:

Moore et al

Abstract:

NASA's New Horizons spacecraft has revealed the complex geology of Pluto and Charon. Pluto's encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection, with a crater retention age no greater than ≈10 Ma. Surrounding terrains show active glacial flow, apparent transport and rotation of large buoyant water-ice crustal blocks, and pitting, likely by sublimation erosion and/or collapse. More enigmatic features include tall mounds with central depressions that are conceivably cryovolcanic, and ridges with complex bladed textures. Pluto also has ancient cratered terrains up to ~4 Ga old that are extensionally fractured and extensively mantled and perhaps eroded by glacial or other processes. Charon does not appear to be currently active, but experienced major extensional tectonism and resurfacing (probably cryovolcanic) nearly 4 billion years ago. Impact crater populations on Pluto and Charon are not consistent with the steepest proposed impactor size-frequency distributions proposed for the Kuiper belt.

Evidence From the Small Moons of Pluto That Charon Formed From a Theia-like Impact With Pluto

The Small Satellites of Pluto as Observed by New Horizons

Authors:

Weaver et al

Abstract:

The New Horizons mission has provided resolved measurements of Pluto's moons Styx, Nix, Kerberos, and Hydra. All four are small, with equivalent spherical diameters of ≈40 km for Nix and Hydra and ~10 km for Styx and Kerberos. They are also highly elongated, with maximum to minimum axis ratios of ≈2. All four moons have high albedos ( ≈50-90 %) suggestive of a water-ice surface composition. Crater densities on Nix and Hydra imply surface ages ≳ 4 Ga. The small moons rotate much faster than synchronous, with rotational poles clustered nearly orthogonal to the common pole directions of Pluto and Charon. These results reinforce the hypothesis that the small moons formed in the aftermath of a collision that produced the Pluto-Charon binary.

Global Albedos of Pluto and Charon from LORRI New Horizons Observations

Global Albedos of Pluto and Charon from LORRI New Horizons Observations

Authors:

Burratti et al

Abstract:

The exploration of the Pluto-Charon system by the New Horizons spacecraft represent the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's "Third Zone" within the context of a geologic world. Images of the entire illuminated surface of Pluto and Charon obtained by the Long Range Reconnaissance Imager (LORRI) camera provide a global map of Pluto that revealed surface albedo variegations larger than any other world except for Saturn's moon Iapetus. Normal reflectances on Pluto range from 0.08-1.0. Charon exhibits a much blander surface with normal reflectances ranging from 0.20-0.73. Pluto's albedo features are well-correlated with geologic features, although some exogenous low-albedo dust may be responsible for features seen to the west of the area informally named Tombaugh Regio. The albedo patterns of both Pluto and Charon are latitudinally organized, with the exception of Tombaugh Regio. The low-albedo areas of Pluto are darker than anything on Charon's surface. The phase curve of Pluto is similar to that of Triton, the large moon of Neptune, and a former KBO dwarf planet, while Charon's is similar to that of the Moon. Preliminary Bond albedos are 0.25 +/- 0.03 for Charon and 0.72 +/- 0.07 for Pluto. Maps of the Bond albedo for both Pluto and Charon are presented for the first time.

The Atmosphere of Pluto

The Atmosphere of Pluto as Observed by New Horizons

Authors:

Gladstone et al

Abstract:

Observations made during the New Horizons flyby provide a detailed snapshot of the current state of Pluto's atmosphere. While the lower atmosphere (at altitudes less than 200 km) is consistent with ground-based stellar occultations, the upper atmosphere is much colder and more compact than indicated by pre-encounter models. Molecular nitrogen (N2) dominates the atmosphere (at altitudes less than 1800 km or so), while methane (CH4), acetylene (C2H2), ethylene (C2H4), and ethane (C2H6) are abundant minor species, and likely feed the production of an extensive haze which encompasses Pluto. The cold upper atmosphere shuts off the anticipated enhanced-Jeans, hydrodynamic-like escape of Pluto's atmosphere to space. It is unclear whether the current state of Pluto's atmosphere is representative of its average state--over seasonal or geologic time scales.

The Icy Spider of Pluto

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Pluto's Bladed Terrain in 3d

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