Cosmic Diary Marchis
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Using a combination of space telescope data, as well as recent data acquired with the SOFIA Airborne telescope and lab experiments, a team of astronomers including researchers from the SETI Institute and Jet Propulsion Laboratory have revealed the presence of dust of exogenic origin at the surface of dwarf planet Ceres. This contamination likely stems from a dust cloud formed in the outer part of the main belt of asteroids following a collision in recent times. That study challenges the relationship proposed between Ceres and asteroids in the C spectral class and instead suggests an origin of this dwarf planet in the transneptunian region. This study was published on January 19 2017 in Astronomical Journal.
Interplanetary dust particles (IDPs), which form meteors when they cross Earth’s atmosphere, represent the largest fraction of extraterrestrial material accreted on Earth. A team led by Pierre Vernazza, research scientist CNRS in the Laboratoire d’Astrophysique de Marseille (LAM – CNRS/AMU), have shown that IDPs are also an important and continuous source of material captured on the surface of asteroids.
Pierre Vernazza explains that « by analyzing the spectral properties of Ceres we have detected material made up of fine particles of dry silicate called pyroxene. However, thermal evolution models proposed for Ceres have predicted a surface composed of aqueously alterated (e.g., clays, carbonates) which was confirmed from recent observations collected by the NASA Dawn mission. Hence the researchers concluded that it is unlikely that those fine grains of dry material could still be preserved in Ceres’ interior.
The team then searched for the possible source of contamination. Recently, observations from a variety of spacecraft have shown that the zodiacal light has significant structure including dust bands which are associated with debris from particular asteroid families, resulting from the destruction of a large asteroid. One of these dust bands produced in the main belt is likely the culprit. In particular, the so-called alpha dust band, produced via grinding within the Beagle family (part of the extended Themis family) formed less than 10 Myrs ago and represents a major source of dust in the outer region of the Main Belt. Recent observations also showed that pyroxene dust is a primordial constituent of the Themis family. Hence the alpha dust band is a plausible source of contamination of Ceres and neighboring asteroids.
If the pyroxene observed on Ceres’ surface is of exogenic origin then this challenges the relationship between Ceres and other Main Belt asteroids which has been inferred for decades based on their similar colors in visible light. Astronomers have classified Ceres and 75% of the asteroids in the so-called spectral class C, suggesting a similar composition. This result shows that the reality is certainly more complex and the detection of ammoniated clays on Ceres suggest a trans-neptunian origin. Evidence for ammonia or ammonium on another dwarf planet, Orcus, strengthens that connection.
This study further suggests that the so far unexplained detection of pyroxenes on metallic asteroids* might also originate from a similar dust source. This process likely acts on a global scale at least in the direct neighborhood of the dust band complicating significantly the work of astronomers who want to understand the composition of asteroids from their color.
« This study resolves a long-time question about the nature of the surface materials inferred from spectroscopic observations in the visible and near infrared, whether they reflect the intrinsic composition of the asteroid or contamination by exogenic material. Our results show that by expanding the study in the mid-infrared the asteroid initial composition remains identifiable despite contamination at a level of ~20%. » added Pierre Vernazza
Franck Marchis, planetary astronomer at the SETI Institute also a co-author of this article, stressed out that “The future of asteroid research would greatly benefit from a systematic study of the largest 400 main-belt asteroids. Based on this result, it is clear that mid-infrared spectroscopic observations are key to understand the true nature of an asteroid. Less than 30 of them were observed by the NASA Spitzer and ESA ISO space-based telescopes, and none can be observed with JWST, the next NASA mid-infrared telescope because they are too bright for its sensitive instrument. A dedicated instrument on board SOFIA airborne telescope or a future dedicated space telescope will reveal the true nature of those asteroids even in the presence of contaminations.”
- SETI PR: http://www.seti.org/seti-institute/press-release/observations-ceres-indicate-asteroids-might-be-camouflaged
- CNRS/LAM PR (en Francais): https://www.lam.fr/les-actualites/article/mise-en-evidence-de-la-contamination-de-la-surface-des-asteroides-par-les?lang=fr
- NASA/SOFIA web article: https://www.nasa.gov/feature/don-t-judge-an-asteroid-by-its-cover-mid-infrared-data-from-sofia-shows-ceres-true
- An interview after my first SOFIA flight in the stratosphere
- Observing in the stratosphere with SOFIA
I co-organized a session for the AGU 2016 meeting entitled “P42A: Solar System Small Bodies: Asteroids, Satellites, Comets, Pluto, and Charon“. Below the info on the session and the schedule.
We have three invited talks that will describe the New Horizons data of Charon, color of Kuiper Belt Object from a ground-based survey and a theoretical study of the formation of the asteroid belt.
Abstract: The composition and physical properties of Small Solar System Bodies
(SSSBs), asteroids and dwarf planets, remnants of the formation of planets, are key to better understand our solar system. Increased knowledge of their surface properties and their potential as resources are also necessary to prepare for robotic and human
exploration. Hints about the internal structure and composition of SSSBs
have been acquired recently thanks to flyby/rendezvous data from space
missions, study of complex multiple asteroid systems, or close encounter
between asteroids. In this session we will discuss results bringing
information on the internal structure and composition of SSSBs based on
space and ground-based data, numerical models, as well as instrument/mission
concepts in the prospect of future exploration.
Chairs and Conveners
Amanda R Hendrix
Planetary Science Institute Tucson
Krishan K Khurana
University of California Los Angeles
Padma A Yanamandra-Fisher
Space Science Institute Rancho Cucamonga
Thursday, 15 December 2016 10:20 – 12:20 Moscone West – 2007
10:20 P42A-01 New Horizons Results at Charon (Invited)
Bonnie J Buratti et al.
10:32 P42A-02 Colours of the Outer Solar System Origins Survey (Col-OSSOS): New Insights into Kuiper belt Surfaces (Invited)
Megan Elizabeth Schwamb et al.
10:44 P42A-03 Pebble Accretion and the Formation of the Asteroid Belt (Invited)
Katherine Kretke et al.
10:56 P42A-04 Constraints for the subsurface structure at the Abydos site on 67P/Churyumov-Gerasimenko resulting from CASSE listening to the MUPUS insertion phase
Martin Knapmeyer et al.
Replaced by P43B-2104 Meteoroid Impact Hazard based on Atmospheric Trajectory Analysis
11:08 P42A-05 Psyche: The Science of a Metal World
Linda T Elkins-Tanton et al.
11:20 P42A-06 Shapes and Densities of the Small Satellites of Pluto
Simon Porter et al.
11:32 P42A-07 CO2 and 12C:13C Isotopic Ratios on Phoebe and Iapetus
Roger Nelson Clark et al.
11:44 P42A-08 Ice Electric: Electron Irradiation Experiments with Porous Water Ice Samples
Andre Galli et al.
11:56 P42A-09 Laboratory Simulations and Spectral Analyses of Space Weathering of Non-Ice Materials on Ocean Worlds
Benjamin R Wing et al.
Moscone South – Poster Hall
P43B-2102 Secular Orbit and Spin Variations of Asteroid (16) Psyche
Bruce G Bills
P43B-2103 Chemistry and Spectroscopy of Frozen Chloride Salts on Icy Bodies
Paul V Johnson
P43B-2104 Meteoroid Impact Hazard based on Atmospheric Trajectory Analysis
P43B-2105 Spectrophotometric Characterisation of the Trojan Asteroids (624) Hektor et (911) Agamemnon
P43B-2106 Shapes and rotational properties of the Select Hilda and Jovian Trojan Asteroids
P43B-2107 Far-UV Spectral and Spatial Analysis from HST Observations of Europa
Tracy M Becker
P43B-2108 CONCAVE SHAPE MODEL OF ASTEROID (130) ELEKTRA BASED ON DISK-RESOLVED IMAGES FROM VLT/SPHERE
P43B-2109 A DIRECT OBSERVATION OF THE ASTEROID’S STRUCTURE FROM DEEP INTERIOR TO REGOLITH: TWO RADARS ON THE AIM MISSION
P43B-2110 Geomorphological Mapping of Sputnik Planum on Pluto: Convection, Glacial Flow, Sublimation and Re-deposition of Nitrogen Ice
Oliver L White
P43B-2111 Constraining the Ice Viscosity and Heat Flux on Enceladus During the Formation of the Leading Hemisphere
Erin Janelle Leonard
P43B-2112 Constraints on the properties of Pluto’s nitrogen-ice rich layer from convection simulations
P43B-2113 Elpasolite Planetary Ice and Composition Spectrometer (EPICS): A Low-Resource Combined Gamma-Ray and Neutron Spectrometer for Planetary Science
Laura C. Stonehill
P43B-2114 Dynamics of HVECs emitted from comet C/2011 L4 as observed by STEREO
Nour E. Raouafi
See you there!
PS: Thanks those who attended the session, as well as the speakers, and my co-chairs (Amanda and Padma).
Here a group picture taken after the session. From left to right: Padma A Yanamandra-Fisher, Maria Gritsevich, Roger Nelson Clark, Andre Galli, Katherine Kretke, Franck Marchis, Megan Elizabeth Schwamb, Benjamin R Wing, Simon Porter, Amanda R Hendrix. Missing on this picture: Bonnie J Buratti & Linda T Elkins-Tanton
AGU Fall meeting is starting tomorrow. I co-organized a session entitled “Detection and Direct Imaging of Habitable Exoplanets: Progress and Future” to discuss the potential of new and future facilities and modeling efforts designed to detect, image and characterize habitable exoplanets, studying their formation, evolution and also the existence of possible biospheres. Topics that are covered in this session include signs of exoplanet habitability and global biosignatures that can be sought with upcoming instrumentation; instrument requirements and technologies to detect these markers; strategies for target selection and prioritization; and impacts of planetary system properties, ground-based and space telescope architectures.
We have two invited talks, one by George Ricker on TESS and a second one by Shawn D Domagal-Goldman on HabEx, two NASA missions that could play a major role on identification and characterization of Earth-Like exoplanets.
Conveners & Chairs:
SETI Institute Mountain View
Ramses M Ramirez
Douglas A. Caldwell
SETI Institute Mountain View
Location: Room 2020 – Moscone West
Schedule of the Talks:
13:40 P13C-01 The Transiting Exoplanet Survey Satellite (TESS): Discovering Exoplanets in the Solar Neighborhood (Invited)
George R. Ricker and TESS Science Team
13:52 P13C-02 HabEx: Finding and characterizing Habitable Exoplanets with a potential future flagship astrophysics mission (Invited)
Shawn D Domagal-Goldman et al.
14:04 P13C-03 Next Generation Telescopes for Terrestrial Exoplanet Characterization
John M Grunsfeld et al.
14:16 P13C-04 Exoplanet detection and characterization with the WFIRST space coronagraph
Bruce Macintosh et al.
14:28 P13C-05 Enhancing Direct Imaging Exoplanet Detection and Characterization with Astrometry
Eduardo Bendek and Ruslan Belikov
14:40 P13C-06 Imaging and characterizing exo-Earths at 10 microns – The TIKI project
Franck Marchis et al.
14:52 P13C-07 Systematic Search of the Nearest Stars for Exoplanetary Radio Emission: VLA observations in L and S Bands
Daniel Winterhalter et al.
15:04 P11A-1845 Modeling Exoplanet Interiors From Host Star Elemental Abundances
Brandi Hamilton and Douglas Green
15:16 P13C-09 Long-Term Stability of Planets in the Alpha Centauri System
Jack J Lissauer and Billy Quarles
15:28 P13C-10 3D Modeling of the H2O Profile of Temperate Earth-Size Planets around Late-Type Stars, and the Signatures in Transit Spectra
Yuka Fujii et al.
Schedule of the Posters:
P11A-1842 Modeling Molecular Hydrogen Emission in M-Dwarf Exoplanetary Systems
William Ray Evonosky et al.
P11A-1843 Feasibility studies for the detection of atomic oxygen exospheres of terrestrial planets in the habitable zone of a low-temperature star with a UV space telescope
Hiroki Horikoshi et al.
P11A-1844 Cloud and Haze in the Atmospheres of Wide-Separation Exoplanets
P11A-1846 Multifractal Analysis of Expoplanetary Spectra
Sahil Agarwal et al.
P11A-1847 By Inferno’s Light: Characterizing TESS Object of Interest Host Stars for Prioritizing Our Search for Habitable Planets
Cayman T Unterborn et al.
P11A-1848 Dysonian SETI as a “Shortcut” to Detecting Habitable Planets
Jason Thomas Wright
See you there,
PS: Unfortunately I did not take a group picture with all our speakers after the session. However, I have a picture taken with our invited speakers. From left to right: Shawn D Domagal-Goldman, Franck Marchis, astronaut John Grunsfeld and George Ricker)