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NASA NTRS2011

Messengers from the Early Solar System - Comets as Carriers of Cosmic Information

Viewed from a cosmic perspective, Earth is a dry planet yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen. Can comets have delivered Earth s water? The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth s water, and for assessing the possible existence of exo-planets similar to Earth. Strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models, imply that comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition. The primary volatiles in comets (ices native to the nucleus) provide the preferred metric, and taxonomies based on them are now beginning to emerge [1, 2, 3]. The measurement of cosmic parameters such as the nuclear spin temperatures for H2O, NH3, and CH4, and of enrichment factors for isotopologues (D/H in water and hydrogen cyanide, N-14/N-15 in CN and hydrogen cyanide) provide additional important tests for the origin of cometary material.

Mumma, Michael J.↗
NASA NTRS2012

Messengers from the Early Solar System - The Similarity and Diversity of Comets

Viewed from a cosmic perspective, Earth is a dry planet yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen. Can comets have delivered Earth's water? The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth's water, and for assessing the possible existence of exo-planets similar to Earth. Strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models, imply that comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition. The primary volatiles in comets (ices native to the nucleus) provide the preferred metric, and taxonomies based on them are now beginning to emerge [1,2,3]. The measurement of cosmic parameters such as the nuclear spin temperatures for H2O, NH3, and CH4, and of enrichment factors for isotopologues (D/H in water and hydrogen cyanide, N-14/N-15 in CN and hydrogen cyanide provide additional important tests for the origin of cometary material. I will provide an overview of these aspects, and their implications for the origin of Earth's water and prebiotic organics.

Mumma, Michael J.↗
NASA NTRS2012

The Volatile Fraction of Comets as Quantified at Infrared Wavelengths - An Emerging Taxonomy and Implications for Natal Heritage

It is relatively easy to identify the reservoir from which a given comet was ejected. But dynamical models demonstrate that the main cometary reservoirs (Kuiper Belt, Oort Cloud) each contain icy bodies that formed in a range of environments in the protoplanetary disk, and the Oort Cloud may even contain bodies that formed in disks of sibling stars in the Sun s birth cluster. The cometary nucleus contains clues to the formative region(s) of its individual components. The composition of ices and rocky grains reflect a range of processes experienced by material while on the journey from the natal interstellar cloud core to the cometary nucleus. For that reason, emphasis is placed on classifying comets according to their native ices and dust (rather than orbital dynamics). Mumma & Charnley [1] reviewed the current status of taxonomies for comets and relation to their natal heritage.

Mumma, M. J.↗
NASA NTRS2008

Triple F - A Comet Nucleus Sample Return Mission

The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA's Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three sample cores of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-andgo sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.

Kueppers, Michael↗
NASA NTRS2013

Micro-ion Traps for Detection of (Pre)-Biotic Organic Compounds on Comets

Comets are currently believed to be a mixture of interstellar and nebular material. Many of the volatiles in comets are attributed to interstellar chemistry, because the same species of carbonaceous compounds are also observed in ices in interstellar molecular (ISM) clouds. Comets are thus likely to be a relatively pristine reservoir of primitive material and carbonaceous compounds in our solar system. They could be a major contributor to the delivery of prebiotic organic compounds, from which life emerged through impacts on early Earth. Mass spectrometers are very powerful tools to identify unknown chemicals, and much progress bas been made in miniaturizing mas spectrometers for space applications. Most miniatu rized mass spectrometers developed to date, however, are still relatively large, power hungry, complicated to assemble, and would have significant impact on space flight vehicle total payload and resource allocations.

vanAmerom, Friso H. W.↗
NASA NTRS2011

Deep Impact, Stardust-NExT and the Behavior of Comet 9P/Tempel 1 from 1997 to 2010

We present observational data for Comet 9P/Tempel 1 taken from 1997 through 2010 in an international collaboration in support of the Deep Impact and Stardust-NExT missions. The data were obtained to characterize the nucleus prior to the Deep Impact 2005 encounter, and to enable us to understand the rotation state in order to make a time of arrival adjustment in February 2010 that would allow us to image at least 25% of the nucleus seen by the Deep Impact spacecraft to better than 80 m/pixel, and to image the crater made during the encounter, if possible. In total, approx.500 whole or partial nights were allocated to this project at 14 observatories worldwide, utilizing 25 telescopes. Seventy percent of these nights yielded useful data. The data were used to determine the linear phase coefficient for the comet in the R-band to be 0.045 +/- 0.001 mag/deg from 1deg to 16deg. Cometary activity was observed to begin inbound near r approx. 4.0 AU and the activity ended near r approx. 4.6 AU as seen from the heliocentric secular light curves, water-sublimation models and from dust dynamical modeling. The light curve exhibits a significant pre- and post-perihelion brightness and activity asymmetry. There was a secular decrease in activity between the 2000 and 2005 perihelion passages of approx. 20%. The post-perihelion light curve cannot be easily explained by a simple decrease in solar insolation or observing geometry. CN emission was detected in the comet at 2.43 AU pre-perihelion, and by r = 2.24 AU emission from C2 and C3 were evident. In December 2004 the production rate of CN increased from 1.8 x 10(exp 23) mol/s to Q(sub CN) = 2.75 x 10(exp 23) mol/s in early January 2005 and 9.3 x 10(exp 24) mol/s on June 6, 2005 at r = 1.53 AU.

Meech, K. J.↗
NASA NTRS2014

Collisional Effects on Magnesium-rich Minerals found in Comets and Asteroids

While generally touted to be the least-altered bodies remaining from the age of the solar system's formation, comets and asteroids have undergone evolutionary processing throughout the 4.5-billion-year lifetime of the solar system. They have suffered the effects of collisions by impactors ranging in size from micrometeoroids to other comets and asteroids. As such, we must ask ourselves: can we detect these evolutionary effects remotely through telescopic observations? With this in mind, a suite of experiments were conducted, impacting magnesium-rich minerals as analogues to those that have been detected in the spectra of both asteroid surfaces and in the dust of cometary comae, including forsterite (Mg2SiO4, olivine), orthoenstatite (Mg2SiO3, pyroxene), diopside (MgCaSi2O6, monoclinic pyroxene), and magnesite (MgCO3, carbonate). These minerals were impacted at velocities ranging from 2.0 km/s to 2.8 km/s using the vertical gun in the Experimental Impact Laboratory (EIL) at NASA Johnson Space Center. These speeds mimic typical velocities of impacts occurring in the Kuiper belt [1]. Two classes of projectile were used: spherical alumina ceramic, whose density mimics that of rock, and cylinders made from the same material that they impacted (e.g., forsterite impactors for forsterite targets, etc.). The peak shock pressure varies significantly, depending on the target and impactor materials and the velocity; thus, shock effects differed in targets impacted at the same velocity but with compositionally different projectiles. The results indicate both: (a) how varying the impactor-density might change the outcome from a scientific viewpoint, as well as (b) possible contamination effects of the ceramic projectile in the resultant spectra of the target minerals from an experimental perspective. Temperature effects were also investigated by impacting samples at both 25 deg. and -25 deg. to: (a) probe whether the varying temperatures experienced by small bodies plays a role in the resultant spectra, and (b) constrain necessary experimental parameters. Analysis of Fourier Transform Infrared (FTIR) spectra obtained from the experimentally shocked materials shows clear indications of spectral shifts in wavelength, as well as a change in relative peak strengths of the spectral signatures at one wavelength compared with another, in all minerals except magnesite. Samples of the forsterite and orthoenstatite that displayed the spectral changes were examined with a transmission electron microscope, which revealed evidence of planar dislocations. The density of the dislocations in the experimentally shocked minerals mimicked the dislocation densities measured in both forsterite and enstatite grains recovered from Comet Wild 2 by the Stardust mission [2, 3, 4]. Further discussion on analyses of peak shock pressure and temperature-dependent effects can be found in Jensen et al., this meeting

Lederer, S.↗
NASA NTRS2014

Collecting Comet Samples by ER-2 Aircraft: Cosmic Dust Collection During the Draconid Meteor Shower in October 2012

Many tons of dust grains, including samples of asteroids and comets, fall from space into the Earth's atmosphere each day. NASA periodically collects some of these particles from the Earth's stratosphere using sticky collectors mounted on NASA's high-flying aircraft. Sometimes, especially when the Earth experiences a known meteor shower, a special opportunity is presented to associate cosmic dust particles with a known source. NASA JSC's Cosmic Dust Collection Program has made special attempts to collect dust from particular meteor showers and asteroid families when flights can be planned well in advance. However, it has rarely been possible to make collections on very short notice. In 2012, the Draconid meteor shower presented that opportunity. The Draconid meteor shower, originating from Comet 21P/Giacobini-Zinner, has produced both outbursts and storms several times during the last century, but the 2012 event was not predicted to be much of a show. Because of these predictions, the Cosmic Dust team had not targeted a stratospheric collection effort for the Draconids, despite the fact that they have one of the slowest atmospheric entry velocities (23 km/s) of any comet shower, and thus offer significant possibilities of successful dust capture. However, radar measurements obtained by the Canadian Meteor Orbit Radar during the 2012 Draconids shower indicated a meteor storm did occur October 8 with a peak at 16:38 (+/-5 min) UTC for a total duration of approximately 2 hours.

Bastien, Ron↗
NASA NTRS2017

Understanding the Effects of Collisional Evolution and Spacecraft Impact Experiments on Comets and Asteroids

Comets and asteroids have endured impacts from other solar system bodies that result in outcomes ranging from catastrophic collisions to regolith evolution due to micrometeorid bombardment of the surface ices and refactory components. Experiments designed to better understand these relics of solar system formation have been conducted on Earth in a laboratory setting, as well as in space through, e.g., the Deep Impact Mission to Comet Tempel 1. Deep Impact fired a high-speed impactor into the roughly 6 km nucleus of the comet. The ejecta plume generated by the impact was studied by both spacecraft instrumentation and groundbased telescopes.

Lederer, S.M.↗
NASA NTRS2016

An Infrared Search for HDO in Comet D/2012 S1 (ISON) and Implications for iSHELL

We performed a sensitive search for HDO in comet D/2012 S1 (ISON) on 2013 November 16, 17, and 22 using CSHELL and the NASA Infrared Telescope Facility. We constrained the HDO/H2O ratio to less than 2.0 VSMOW (the terrestrial ocean value) at the 3 sigma uncertainty level from two independent measurements corresponding to different H2O outgassing rates. This represents the best constrained HDO/H2O ratio for a comet using a small (3 m) telescope and illustrates that when CSHELL is replaced with iSHELL, 3 m class telescopes are still strong contenders for detecting minor volatile species in moderately bright comets.

Gibb, Erika L.↗
NASA NTRS2017

Development and Testing of Harpoon-Based Approaches for Collecting Comet Samples (Video Supplement)

This video supplement contains a set of videos created during the approximately 10-year-long course of developing and testing the Goddard Space Flight Center (GSFC) harpoon-based approach for collecting comet samples. The purpose of the videos is to illustrate various design concepts used in this method of acquiring samples of comet material, the testing used to verify the concepts, and the evolution of designs and testing. To play the videos this PDF needs to be opened in the freeware Adobe Reader. They do not seem to play while within a browser. While this supplement can be used as a stand-alone document, it is intended to augment its parent document of the same title, Development and Testing of Harpoon-Based Approaches for Collecting Comet Samples (NASA/CR-2017-219018; this document is accessible from the website: https://ssed.gsfc.nasa.gov/harpoon/SAS_Paper-V1.pdf). The parent document, which only contains text and figures, describes the overall development and testing effort and contains references to each of the videos in this supplement. Thus, the videos are primarily intended to augment the information provided by the text and figures in the parent document. This approach was followed to allow the file size of the parent document to remain small enough to facilitate downloading and storage. Some of the videos were created by other organizations, Johns Hopkins University Applied Physics Laboratory (JHU APL) and the German Aerospace Center called, the Deutsches Zentrum für Luft- und Raumfahrt (DLR), who are partnering with GSFC on developing this technology. Each video is accompanied by text that provides a summary description of its nature and purpose, as well as the identity of the authors. All videos have been edited to only show key parts of the testing. Although not all videos have sound, the sound has been retained in those that have it. Also, each video has been given one or more title screens to clarify what is going in different phases of the video.

Purves, Lloyd↗
NASA NTRS2017

Evidence of Collisional Histories of Asteroids, Comets and Meteorites: Comparisons with Shocked Minerals

Evidence of the collisional history of comets and asteroids has been emerging from analyses of cometary forsterite and enstatite returned from Comet Wild 2 by the Stardust mission (Keller et al.Geochim. Cosmochim. Acta 72, 2008; Tomeoka et al. MAPS 43, 2008; Jacobs et al. MAPS 44, 2009). Likewise, shock metamorphism is observed in many meteoritic forsterites and enstatites (McCausland et al. AGU, 2010), suggesting similar collisional histories for asteroids. Further exploration of the effects of collisions is slated for the upcoming Asteroid Impact Mission/Double Asteroid Redirection Test (AIM/DART) mission, expected for launch in 2020. DART will impact Didymoon, the companion of the larger 65803 Didymos (1996 G2) asteroid, and AIM will use its instrumentation to characterize the impact. A suite of relevant impact experiments have been carried out in the Experimental Impact Laboratory at the NASA Johnson Space Center at velocities ranging from approx. 2.0 - 2.8 km/s and temperatures from 25 C to -100 C. Targets include a suite of minerals typically found in cometary dust and in asteroids and meteorites: Mg-rich forsterite (olivine), enstatite (orthopyroxene), diopside (clinopyroxene), magnesite (Mg-rich carbonate), and serpentine (phyllosilicate). Transmission Electron Microscope (TEM) imaging indicates evidence of shock similar to that seen in forsterite and enstatite from Comet Wild 2. Fourier Transform Infrared (FTIR) Spectroscopy will also be used for comparisons with meteorite spectra. A quantitative analysis of the shock pressures required to induce planar dislocations and spectral effects with respect to wavelength will also be presented.

Lederer, Susan M.↗
NASA NTRS2015

Plasma Waves Associated with Mass-Loaded Comets

Plasma waves and instabilities are integrally involved with the plasma "pickup" process and the mass loading of the solar wind (thus the formation of ion tails and the magnetic tails). Anisotropic plasmas generated by solar wind-comet interactions (the bow shock, magnetic field pileup) cause the generation of plasma waves which in turn "smooth out" these discontinuities. The plasma waves evolve and form plasma turbulence. Comets are perhaps the best "laboratories" to study waves and turbulence because over time (and distance) one can identify the waves and their evolution. We will argue that comets in some ways are better laboratories than magnetospheres, interplanetary space and fusion devices to study nonlinear waves and their evolution.

instabilities↗
NASA NTRS2018

Direct Characterization of Comets and Asteroids via Cosmic Dust Analysis from the Deep Space Gateway

The Deep Space Gateway (DSG) may provide a platform for direct sampling of a large number of comets and asteroids, through employment of an instrument for characterizing dust from these bodies. Every year, the Earth traverses through debris streams of dust and small particles from comets and asteroids in Earth-crossing orbits, generating short-lived outbursts of meteor activity commonly known as "meteor showers" (Figure 1). The material in each debris stream originates from a distinct parent body, many of which have been identified. By sampling this material, it is possible to quantitatively analyze the composition of a dozen or more comets and asteroids (See Figure 2, following page) without leaving cislunar space.

Fries, M.↗
NASA NTRS2017

Hypervolatiles in a Jupiter-Family Comet: Observations of 45P/Honda-Mrkos-Pajdusakova Using iSHELL at the NASA-IRTF

We used the new high spectral resolution cross-dispersed facility spectrograph, iSHELL, at the NASA Infrared Telescope Facility on Maunakea, HI, to observe Jupiter-family comet (JFC) 45P/Honda-Mrkos-Pajdusakova. We report water production rates, as well as production rates and abundance ratios relative to H2O, for eight trace parent molecules (native ices), CO, CH4, H2CO, CH3OH, HCN, NH3, C2H2, and C2H6, on 2 days spanning UT 2017 January 6/7 and 7/8, shortly following perihelion. Trace species were measured simultaneously with H2O and/or OH prompt emission, a proxy for H2O production, thereby providing a robust and consistent means of establishing the native ice composition of 45P. Its favorable geocentric radial velocity (approximately minus 35 kilometers per second) permitted sensitive measures of the "hypervolatiles" CO and CH4, which are substantially undercharacterized in JFCs. Our results represent the most precise ground-based measures of CO and CH4 to date in a JFC, providing a foundation for building meaningful statistics regarding their abundances. The abundance ratio for CH4 in 45P (0.79 percent plus or minus 0.06 percent relative to H2O) was consistent with its median value as measured among Oort Cloud comets, whereas CO (0.60 percent plus or minus 0.04 percent) was strongly depleted. Compared with all measured comets, HCN (0.049 percent plus or minus 0.012 percent) was strongly depleted, CH3OH (3.6 percent plus or minus 0.3 percent) was enriched, and the remaining species were consistent with their respective median abundances. The volatile composition measured for 45P could indicate processing of ices prior to their incorporation into its nucleus. Spatial analysis of emissions suggests enhanced release of more volatile species into the sunward-facing hemisphere of the coma.

DiSanti, Michael A.↗
NASA NTRS2017

Interplanetary Coronal Mass Ejection Observed at STEREO-A, Mars, Comet 67P/Churyumov-Gerasimenko, Saturn,and New Horizons En Route to Pluto: Comparison of Its Forbush Decreases at 1.4, 3.1, and 9.9 AU

We discuss observations of the journey throughout the Solar System of a large interplanetary coronal mass ejection (ICME) that was ejected at the Sun on 14 October 2014. The ICME hit Mars on 17 October, as observed by the Mars Express, Mars Atmosphere and Volatile EvolutioN Mission (MAVEN), Mars Odyssey, and Mars Science Laboratory (MSL) missions, 44 h before the encounter of the planet with the Siding-Spring comet, for which the space weather context is provided. It reached comet 67P/Churyumov-Gerasimenko, which was perfectly aligned with the Sun and Mars at 3.1 AU, as observed by Rosetta on 22 October. The ICME was also detected by STEREO-A on 16 October at 1 AU, and by Cassini in the solar wind around Saturn on the 12 November at 9.9 AU. Fortuitously, the New Horizons spacecraft was also aligned with the direction of the ICME at 31.6 AU. We investigate whether this ICME has a nonambiguous signature at New Horizons. A potential detection of this ICME by Voyager 2 at 110-111 AU is also discussed. The multispacecraft observations allow the derivation of certain properties of the ICME, such as its large angular extension of at least 116deg, its speed as a function of distance, and its magnetic field structure at four locations from 1 to 10 AU. Observations of the speed data allow two different solar wind propagation models to be validated. Finally, we compare the Forbush decreases (transient decreases followed by gradual recoveries in the galactic cosmic ray intensity) due to the passage of this ICME at Mars, comet 67P, and Saturn.

Witasse, O.↗
NASA NTRS2018

Comet C/2013 V5 (Oukaimeden): Evidence for Depleted Organic Volatiles and Compositional Heterogeneity as Revealed through Infrared Spectroscopy

We obtained high-resolution (lambda divided by delta times lambda equals approximately 25,000) pre-perihelion spectra of Comet C/2013 V5 (Oukaimeden) using NIRSPEC at Keck II on UT 2014 September 5-6, and CSHELL (Cryogenic Echelle Spectrograph) at the NASA-Infrared Telescope Facility on September 11-13, altogether spanning a range in heliocentric distance R (sub h) equals 0.789-0.698 astronomical units. We report water production rates, and production rates and abundance ratios relative to co-measured H2O for eight trace molecules: CO, H2CO, CH3OH, CH4, C2H2, C2H6, HCN, and NH3. Our measured water production rates from NIRSPEC ( Near Infra-Red Spectrograph) and CSHELL observations remained relatively constant and were close to those from SOHO (Solar and Heliospheric Observatory) / Solar Wind Anisotropies observations that encompassed our dates, suggesting H2O production dominated by release directly from or within approximately 2000 kilometers of the nucleus. All trace volatiles were depleted relative to their respective median abundances among comets, excepting NH3, which was consistent with its median abundance. Most surprising were pronounced increases in abundance ratios for CH3OH (by 51 percent relative to simultaneously measured H2O) and especially C2H6 (by 87 percent) between September 5 and 6. On September 5, C2H6 was severely depleted, consistent with its lowest abundance yet measured for any comet. It also tracked the spatial profile of H2O, suggesting C2H6 was associated with a polar ice phase dominating gas production. On September 6, C2H6 was only moderately depleted and was spatially distinct from H2O, suggesting both polar- and nonpolar-dominated ice phases contributed to the activity then. Our results are consistent with a nonhomogeneous volatile composition for C/2013V5, implying differential processing of its constituent ices.

DiSanti, Michael A.↗
NASA NTRS2019

The CAESAR New Frontiers Mission: 1. Expected Nature of the Returned Comet Sample

Comets are time capsules from the birth of our Solar System that record pre-solar history, the initial stages of planet formation, and the sources of prebiotic organics and volatiles for the origin of life. These capsules can only be opened in laboratories on Earth. CAESAR (Comet Astrobiology Exploration Sample Return)’s sample analysis objectives are to understand the nature of Solar System starting materials and how these components came together to form planets and give rise to life. Examination of these comet nucleus surface samples in laboratories around the world will also provide ground truth to remote observations of the innumerable icy bodies of the Solar System.

Lauretta, D. S.↗