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All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Titan haze: structure and properties of cyanoacetylene and cyanoacetylene-acetylene photopolymers

The structure and morphological properties of polymers produced photochemically from the UV irradiation of cyanoacetylene and cyanoacetylene mixtures have been examined to evaluate their possible contribution to the haze layers found on Titan. A structural analysis of these polymers may contribute to our understanding of the data returned from the Huygens probe of the Cassini mission that will pass through the atmosphere of Titan in the year 2004. Infrared analysis, elemental analysis, and thermal methods (thermogravimetric analysis, thermolysis, pyrolysis) were used to examine structures of polycyanoacetylenes produced by irradiation of the gas phase HC3N at 185 and 254 nm. The resulting brown to black polymer, which exists as small particles, is believed to be a branched chain of conjugated carbon-carbon double bonds, which, on exposure to heat, cyclizes to form a graphitic structure. Similar methods of analysis were used to show that when HC3N is photolyzed in the presence of Titan's other atmospheric constituents (CH4, C2H6, C2H2, and CO), a copolymer is formed in which the added gases are incorporated as substituents on the polymer chain. Of special significance is the copolymer of HC3N and acetylene (C2H2). Even in experiments where C2H2 was absorbing nearly all of the incident photons, the ratio of C2H2 to HC3N found in the resulting polymer was only 2:1. Scanning electron microscopy was used to visually examine the polymer particles. While pure polyacetylene particles are amorphous spheres roughly 1 micrometer in diameter, polycyanoacetylenes appear to be strands of rough, solid particles slightly smaller in size. The copolymer of HC3N and C2H2 exhibits characteristics of both pure polymers. This is particularly important as pure polyacetylenes do not match the optical constants measured for Titan's atmospheric hazes. The copolymers produced by the incorporation of other minor atmospheric constituents, like HC3N, into the polyacetylenes are expected to have optical constants more comparable to those of the Titan haze.

Non-NASA Center↗
NASA NTRS1996

Simulations of Titan's brightness by a two-dimensional haze model

We have used a 2-D microphysics model to study the effects of atmospheric motions on the albedo of Titan's thick haze layer. We compare our results to the observed variations of Titan's brightness with season and latitude. We use two wind fields; the first is a simple pole-to-pole Hadley cell that reverses twice a year. The second is based on the results of a preliminary Titan GCM. Seasonally varying wind fields, with horizontal velocities of about 1 cm sec-1 at optical depth unity, are capable of producing the observed change in geometric albedo of about 10% over the Titan year. Neither of the two wind fields can adequately reproduce the latitudinal distribution of reflectivity seen by Voyager. At visible wavelengths, where only haze opacity is important, upwelling produces darkening by increasing the particle size at optical depth unity. This is due to the suspension of larger particles as well as the lateral removal of smaller particles from the top of the atmosphere. At UV wavelengths and at 0.89 micrometers the albedo is determined by the competing effects of the gas the haze material. Gas is bright in the UV and dark at 0.89 micrometers. Haze transport at high altitudes controls the UV albedo and transport at low altitude controls the 0.89 micrometers albedo. Comparisons between the hemispheric contrast at UV, visible, and IR wavelengths can be diagnostic of the vertical structure of the wind field on Titan.

NASA Discipline Exobiology↗
NASA NTRS1992

Titan: a laboratory for prebiological organic chemistry

When we examine the atmospheres of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune), the satellites in the outer solar system, comets, and even--through microwave and infrared spectroscopy--the cold dilute gas and grains between the stars, we find a rich organic chemistry, presumably abiological, not only in most of the solar system but throughout the Milky Way galaxy. In part because the composition and surface pressure of the Earth's atmosphere 4 x 10(9) years ago are unknown, laboratory experiments on prebiological organic chemistry are at best suggestive; but we can test our understanding by looking more closely at the observed extraterrestrial organic chemistry. The present Account is restricted to atmospheric organic chemistry, primarily on the large moon of Saturn. Titan is a test of our understanding of the organic chemistry of planetary atmospheres. Its atmospheric bulk composition (N2/CH4) is intermediate between the highly reducing (H2/He/CH4/NH3/H2O) atmospheres of the Jovian planets and the more oxidized (N2/CO2/H2O) atmospheres of the terrestrial planets Mars and Venus. It has long been recognized that Titan's organic chemistry may have some relevance to the events that led to the origin of life on Earth. But with Titan surface temperatures approximately equal to 94 K and pressures approximately equal to 1.6 bar, the oceans of the early Earth have no ready analogue on Titan. Nevertheless, tectonic events in the water ice-rich interior or impact melting and slow re-freezing may lead to an episodic availability of liquid water. Indeed, the latter process is the equivalent of a approximately 10(3)-year-duration shallow aqueous sea over the entire surface of Titan.

Non-NASA Center↗
NASA NTRS2004

A SIFT ion-molecule study of some reactions in Titan's atmosphere. reactions of N(+), N(2)(+), and HCN(+) with CH(4), C(2)H(2), and C(2)H(4)

The results of a study of the ion-molecule reactions of N(+), N(2)(+), and HCN(+) with methane, acetylene, and ethylene are reported. These studies were performed using the FA-SIFT at the University of Canterbury. The reactions studied here are important to understanding the ion chemistry in Titan's atmosphere. N(+) and N(2)(+) are the primary ions formed by photo-ionization and electron impact in Titan's ionosphere and drive Titan's ion chemistry. It is therefore very important to know how these ions react with the principal trace neutral species in Titan's atmosphere: Methane, acetylene, and ethylene. While these reactions have been studied before the product channels have been difficult to define as several potential isobaric products make a definitive answer difficult. Mass overlap causes difficulties in making unambiguous species assignments in these systems. Two discriminators have been used in this study to resolve the mass overlap problem. They are deuterium labeling and also the differences in reactivities of each isobar with various neutral reactants. Several differences have been found from the products in previous work. The HCN(+) ion is important in both Titan's atmosphere and in the laboratory.

Extraterrestrial Environment/chemistry↗
NASA NTRS2005

Preliminary Interpretation of Titan Plasma Interaction as Observed by the Cassini Plasma Spectrometer: Comparisons With Voyager 1

The Cassini Plasma Spectrometer (CAPS) instrument made measurements of Titan s plasma environment when the Cassini Orbiter flew through the moon s plasma wake October 26,2004 (flyby TA) and December 13,2004 (flyby TB). Preliminary CAPS ion and electron measurements from these encounters (1,2) are compared with measurements made by the Voyager I Plasma Science Instrument (PLS). The comparisons are used to evaluate previous interpretations and predictions of the Titan plasma environment that have been made using PLS measurements (3,4). The plasma wake trajectories of flybys TA, TB and Voyager 1 are similar because they occurred when Titan was near Saturn s local noon. These similarities make possible direct, meaningful comparisons between the various plasma wake measurements. The inquiries stimulated by the previous interpretations and predictions made using PLS data have produced the following results from the CAPS ion measurements: A) The major ambient ion components of Saturn s rotating magnetosphere in the vicinity of Titan are H+, H2+, and O+. B) Finite gyroradius effects are apparent in ambient 0 as the result of its interaction with Titan s atmosphere. C) The principal pickup ions are composed of H+, H2+, CH4+ and N2+. D) There is clear evidence of slowing down of the ambient plasma due to pickup ion mass loading; and, as the ionopause~ is approached, heavier pickup ions such as N2+ become dominant. The similarities and differences between the magnitudes and structures of the electron densities and temperatures along the three flyby trajectories are described

Hartle, R. E.↗
NASA NTRS2005

Theoretical Calculations on Sediment Transport on Titan, and the Possible Production of Streamlined Forms

The Cassini Imaging Science System (ISS) has been returning images of Titan, along with other Saturnian satellites. Images taken through the 938 nm methane window see down to Titan's surface. One of the purposes of the Cassini mission is to investigate possible fluid cycling on Titan. Lemniscate features shown recently and radar evidence of surface flow prompted us to consider theoretically the creation by methane fluid flow of streamlined forms on Titan. This follows work by other groups in theoretical consideration of fluid motion on Titan's surface.

Burr, D. M.↗
NASA NTRS2005

Intensive Titan exploration begins

The Cassini Orbiter spacecraft first skimmed through the tenuous upper atmosphere of Titan on 26 October 2004. This moon of Saturn is unique in our solar system, with a dense nitrogen atmosphere that is cold enough in places to rain methane, the feedstock for the atmospheric chemistry that produces hydrocarbons, nitrile compounds, and Titan's orange haze. The data returned from this flyby supply new information on the magnetic field and plasma environment around Titan, expose new facets of the dynamics and chemistry of Titan's atmosphere, and provide the first glimpses of what appears to be a complex, fluid-processed, geologically young Titan surface.

Spacecraft↗
NASA NTRS2004

Processing Techniques Developed to Fabricate Lanthanum Titanate Piezoceramic Material for High-Temperature Smart Structures

Piezoelectric ceramic materials are potential candidates for use as actuators and sensors in intelligent gas turbine engines. For piezoceramics to be applied in gas turbine engines, they will have to be able to function in temperatures ranging from 1000 to 2500 F. However, the maximum use temperature for state-of-the-art piezoceramic materials is on the order of 300 to 400 F. Research activities have been initiated to develop high-temperature piezoceramic materials for gas turbine engine applications. Lanthanum titanate has been shown to have high-temperature piezoelectric properties with Curie temperatures of T(sub c) = 1500 C and use temperatures greater than 1000 C. However, the fabrication of lanthanum titanate poses serious challenges because of the very high sintering temperatures required for densification. Two different techniques have been developed at the NASA Glenn Research Center to fabricate dense lanthanum titanate piezoceramic material. In one approach, lower sintering temperatures were achieved by adding yttrium oxide to commercially available lanthanum titanate powder. Addition of only 0.1 mol% yttrium oxide lowered the sintering temperature by as much as 300 C, to just 1100 C, and dense lanthanum titanate was produced by pressure-assisted sintering. The second approach utilized the same commercially available powders but used an innovative sintering approach called differential sintering, which did not require any additive.

Goldsby, Jon C.↗
NASA NTRS2006

Titan's Atmospheric Composition from Observations by the Cassini Infrared Spectrometer

The Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft has been making observations during the fly-bys of Titan since the Saturn-Orbit-Insertion in July 2004. The observations provide infrared them1 emission spectra of Titan s atmosphere in three spectral channels covering the 10/cm to 1400/cm spectral region, with variable spectral resolutions of 0.53/cm and 2.8/cm. The uniquely observed spectra exhibit rotational and vibrational-rotational spectral lines of the molecular constituents of Titan s atmosphere that may be analyzed to retrieve information about the composition, thermal structure, and physical and dynamical processes in the remotely sensed atmosphere. We present an analysis of Titan's infrared spectra observed during July 2004 (TO), December 2004 (Tb) and February 2005 (T3), for retrieval of the stratospheric thermal structure, distribution of the hydrocarbons, nitriles, and oxygen bearing constituents, such as C2H2, C2H4, C2H6, C3H8, HCN, HC3N, CO, and CO2 . Preliminary results on the distribution and opacity of haze in Titan s atmosphere are discussed.

Abbas, M. M.↗
NASA NTRS2006

Design of a Long Endurance Titan VTOL Vehicle

Saturn s moon Titan promises insight into many key scientific questions, many of which can be investigated only by in situ exploration of the surface and atmosphere of the moon. This research presents a vertical takeoff and landing (VTOL) vehicle designed to conduct a scientific investigation of Titan s atmosphere, clouds, haze, surface, and any possible oceans. In this investigation, multiple options for vertical takeoff and horizontal mobility were considered. A helicopter was baselined because of its many advantages over other types of vehicles, namely access to hazardous terrain and the ability to perform low speed aerial surveys. Using a nuclear power source and the atmosphere of Titan, a turbo expander cycle produces the 1.9 kW required by the vehicle for flight and operations, allowing it to sustain a long range, long duration mission that could traverse the majority of Titan. Such a power source could increase the lifespan and quality of science for planetary aerial flight to an extent that the limiting factor for the mission life is not available power but the life of the mechanical parts. Therefore, the mission could potentially last for years. This design is the first to investigate the implications of this potentially revolutionary technology on a Titan aerial vehicle.

Prakash, Ravi↗
NASA NTRS2006

Titan Ion Composition at Magnetosphere-Ionosphere Transition Region

Using Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS) ion composition data, we will investigate the compositional changes at the transition region between Saturn's magnetospheric flow and Titan's upper ionosphere. It is this region where scavenging of Titan's upper ionosphere can occur, where it is then dragged away by the magnetospheric flow as cold plasma for Saturn's magnetosphere. This cold plasma may form plumes as originally proposed by (1) during the Voyager 1 epoch. This source of cold plasma may have a unique compositional signature such as methane group ions. Water group ions that are observed in Saturn's outer magnetosphere (2,3) are relatively hot and probably come from the inner magnetosphere where they are born from fast neutrals escaping Enceladus (4) and picked up in the outer magnetosphere as hot plasma (5). This scenario will be complicated by pickup methane ions within Titan's mass loading region, as originally predicted by (6) based on Voyager 1 data and observationally confirmed by (3,7) using CAPS IMS data. But, CH4(+) ions or their fragments can only be produced as pickup ions from Titan's exosphere which can extend beyond the transition region of concern here, while CH5(+) ions can be scavenged from Titan's ionosphere. We will investigate these possibilities.

Sittler, Edward C.↗
NASA NTRS2007

An Attempt to Observe Debris from the Breakup of a Titan 3C-4 Transtage

In February 2007 dedicated observations were made of the orbital space predicted to contain debris from the breakup of the Titan 3C-4 transtage back on February 21, 1992. These observations were carried out on the Michigan Orbital DEbris Survey Telescope (MODEST) in Chile with its 1.3deg field of view. The search region or orbital space (inclination and right ascension of the ascending node (RAAN) was predicted using NASA#s LEGEND (LEO-to-GEO Environment Debris) code to generate a Titan debris cloud. Breakup fragments are created based on the NASA Standard Breakup Model (including fragment size, area-to-mass (A/M), and delta-V distributions). Once fragments are created, they are propagated forward in time with a subroutine GEOPROP. Perturbations included in GEOPROP are those due to solar/lunar gravity, radiation pressure, and major geopotential terms. Barker, et. al, (AMOS Conference Proceedings, 2006, pp. 596-604) used similar LEGEND predictions to correlate survey observations made by MODEST (February 2002) and found several possible night-to-night correlations in the limited survey dataset. One conc lusion of the survey search was to dedicate a MODEST run to observing a GEO region predicted to contain debris fragments and actual Titan debris objects (SSN 25000, 25001 and 30000). Such a dedicated run was undertaken with MODEST between February 17 and 23, 2007 (UT dates). MODEST#s limiting magnitude of 18.0 (S\N approx.10) corresponds to a size of 22cm assuming a diffuse Lambertian albedo of 0.2. However, based on observed break-up data, we expect most debris fragments to be smaller than 22cm which implies a need to increase the effective sensitivity of MODEST for smaller objects. MODEST#s limiting size can be lowered by increasing the exposure time (20 instead of 5 seconds) and applying special image processing. The special processing combines individual CCD images to detect faint objects that are invisible on a single CCD image. Sub-images are cropped from six consecutive CCD images with pixel shifts between images being consistent with the predicted movement of a Titan object. A median image of all the sub-images is then created leaving only those objects with the proper Titan motion. Limiting the median image in this manner brings the needed computer time to process all images taken on one night down to about 50 hours of CPU time.

Barker, E. S.↗
NASA NTRS2006

Titan Explorer Entry, Descent and Landing Trajectory Design

The Titan Explorer mission concept includes an orbiter, entry probe and inflatable airship designed to take remote and in-situ measurements of Titan's atmosphere. A modified entry, descent and landing trajectory at Titan that incorporates mid-air airship inflation (under a parachute) and separation is developed and examined for Titan Explorer. The feasibility of mid-air inflation and deployment of an airship under a parachute is determined by implementing and validating an airship buoyancy and inflation model in the trajectory simulation program, Program to Optimize Simulated Trajectories II (POST2). A nominal POST2 trajectory simulation case study is generated which examines different descent scenarios by varying airship inflation duration, orientation, and separation. The buoyancy model incorporation into POST2 is new to the software and may be used in future trajectory simulations. Each case from the nominal POST2 trajectory case study simulates a successful separation between the parachute and airship systems with sufficient velocity change as to alter their paths to avoid collision throughout their descent. The airship and heatshield also separate acceptably with a minimum distance of separation from the parachute system of 1.5 km. This analysis shows the feasibility of airship inflation on a parachute for different orientations, airship separation at various inflation times, and preparation for level-flight at Titan.

Fisher, Jody L.↗
NASA NTRS2009

Saturn's Magnetosphere and Properties of Upstream Flow at Titan: Preliminary Results

Using Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS) measurements, we present the ion fluid properties and its ion composition of the upstream flow for Titan's interaction with Saturn's magnetosphere. A 3D ion moments algorithm is used which is essentially model independent with only requirement is that ion flow is within the CAPS IMS 2(pi) steradian field-of-view (FOV) and that the ion 'velocity distribution function (VDF) be gyrotropic. These results cover the period from TA flyby (2004 day 300) to T22 flyby (2006 363). Cassini's in situ measurements of Saturn's magnetic field show it is stretched out into a magnetodisc configuration for Saturn Local Times (SLT) centered about midnight local time. Under those circumstances the field is confined near the equatorial plane with Titan either above or below the magnetosphere current sheet. Similar to Jupiter's outer magnetosphere where a magnetodisc configuration applies, one expects the heavy ions within Saturn's outer magnetosphere to be confined within a few degrees of the current sheet while at higher magnetic latitudes protons should dominate. We show that when Cassini is between dusk-midnight-dawn local time and spacecraft is not within the current sheet that light ions (H, 142) tend to dominate the ion composition for the upstream flow. If true, one may expect the interaction between Saturn's magnetosphere, locally devoid of heavy ions and Titan's upper atmosphere and exosphere to be significantly different from that for Voyager 1, TA and TB when heavy ions were present in the upstream flow. We also present observational evidence for Saturn's magnetosphere interaction with Titan's extended H and H2 corona which can extend approx. 1 Rs from Titan.

Sittler, E. C., Jr.↗
NASA NTRS2006

ARPS Enabled Titan Rover Concept with Inflatable Wheels

The Decadal Survey identified Titan as one of the top priority science destinations in the large moons category, while NASA's proposed Design Reference Mission Set ranked a Titan in-situ explorer second, after a recommended Europa Geophysical Observer mission. This paper discusses a Titan rover concept, enabled by a single advanced Radioisotope Power System that could provide about 110We (BOL). The concept targets the smaller Flagship or potentially the New Frontiers mission class. This MSL class rover would traverse on four 1.5 m diameter inflatable wheels during its 3 years mission duration and would use as much design and flight heritage as possible to reduce mission cost. Direct to Earth communication would remove the need for a relay orbiter. Details on the strawman instrument payload, and rover subsystems are given for this science driven mission concept. In addition, power system trades between Advanced RTG, TPV, and Advanced Stirling and Brayton Radioisotope Power Systems (RPS) are outlined. While many possible approaches exist for Titan in-situ exploration, the Titan rover concept presented here could provide a scientifically interesting and programmatically affordable solution.

Radioisotope Power System (RPS)↗
NASA NTRS2011

Investigating the Chemical Pathways to PAH- and PANH-Based Aerosols in Titan's Atmospheric chemistry

A complex organic chemistry between Titan's two main constituents, N2 and CH4, leads to the production of more complex molecules and subsequently to solid organic aerosols. These aerosols are at the origin of the haze layers giving Titan its characteristic orange color. In situ measurements by the Ion Neutral Mass Spectrometer (INMS) and Cassini Plasma Spectrometer (CAPS) instruments onboard Cassini have revealed the presence of large amounts of neutral, positively and negatively charged heavy molecules in the ionosphere of Titan. In particular, benzene (C6H6) and toluene (C6H5CH3), which are critical precursors of polycyclic aromatic hydrocarbon (PAH) compounds, have been detected, suggesting that PAHs might play a role in the production of Titan s aerosols. Moreover, results from numerical models as well as laboratory simulations of Titan s atmospheric chemistry are also suggesting chemical pathways that link the simple precursor molecules resulting from the first steps of the N2-CH4 chemistry (C2H2, C2H4, HCN ...) to benzene, and to PAHs and nitrogen-containing PAHs (or PANHs) as precursors to the production of solid aerosols.

Sciamma-O'Brien, Ella Marion↗
NASA NTRS2013

Observations of Titan 3C-4 Transtage Fragmentation Debris

The fragmentation of a Titan 3C-4 Transtage (1968-081) on 21 February 1992 is one of only two known break-ups in or near geosynchronous orbit. The original rocket body and 24 pieces of debris are currently being tracked by the US Space Surveillance Network (SSN). The rocket body (SSN# 3432) and several of the original fragments (SSN# 25000, 25001, 30000, and 33511) were observed in survey mode during 2004-2010 using the 0.6-m Michigan Orbital DEbris Survey Telescope (MODEST) in Chile using a broad R filter. This paper will present a size distribution for all calibrated magnitude data acquired on MODEST. Size distribution plots will also be shown using historical models for small fragmentation debris (down to 10 cm) believed to be associated with the Titan break-up. In November 2010, visible broadband photometry (Johnson/Kron-Cousins BVRI) was acquired with the 0.9-m Small and Moderate Aperture Research Telescope System (SMARTS) at the Cerro Tololo Inter-American Observatory (CTIO) in Chile on several Titan fragments (SSN# 25001, 33509, 33510) and the parent rocket body. Color index data will be used to determine the fragment brightness distribution and how the data compares to spacecraft materials measured in the laboratory using similar photometric measurement techniques. In 2012, the SSN added 16 additional fragments to the catalogue. MODEST acquired magnitude data on ten Titan fragments in late 2012 and early 2013. The magnitude distribution of all the observed fragments are analyzed as a function of time. In order to better characterize the breakup fragments spectral measurements were acquired on the original rocket body and five Titan fragments using the 6.5-m Magellan telescopes at Las Campanas Observatory in Chile. The telescopic spectra are compared with laboratory acquired spectra of materials (e.g., Aluminum and various paints) and categorized based on known absorption features for spacecraft materials.

Cowardin, Heather↗
NASA NTRS2013

Crater Topography on Titan: Implications for Landscape Evolution

We present a comprehensive review of available crater topography measurements for Saturn's moon Titan. In general, the depths of Titan's craters are within the range of depths observed for similarly sized fresh craters on Ganymede, but several hundreds of meters shallower than Ganymede's average depth vs. diameter trend. Depth-to-diameter ratios are between 0.0012 +/- 0.0003 (for the largest crater studied, Menrva, D approximately 425 km) and 0.017 +/- 0.004 (for the smallest crater studied, Ksa, D approximately 39 km). When we evaluate the Anderson-Darling goodness-of-fit parameter, we find that there is less than a 10% probability that Titan's craters have a current depth distribution that is consistent with the depth distribution of fresh craters on Ganymede. There is, however, a much higher probability that the relative depths are uniformly distributed between 0 (fresh) and 1 (completely infilled). This distribution is consistent with an infilling process that is relatively constant with time, such as aeolian deposition. Assuming that Ganymede represents a close 'airless' analogue to Titan, the difference in depths represents the first quantitative measure of the amount of modification that has shaped Titan's surface, the only body in the outer Solar System with extensive surface-atmosphere exchange.

Implications↗