Timothy N. Titus

Timothy N. Titus
United States Geological Survey | USGS · Astrogeology Science Center

Doctorate

About

310
Publications
21,347
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Introduction
I am currently working with MGS TES, M01 THEMIS, MRO CRISM observations to constrain interannual variation of the Martian seasonal polar caps. In addition to polar processes, we also maintain the Mars Global Digital Dune Database. The 4th Dune Workshop is approaching. I am working with Dawn VIR observations to constrain the thermal inertia of the surface of asteroid 4 Vesta. I am working with the USGS ISIS programming staff to increase the # of spacecraft missions supported by ISIS software.
Additional affiliations
June 1999 - present
United States Geological Survey
Position
  • Supervisory Research Space Scientist
September 1996 - March 1997
University of Wyoming
Position
  • Staff Lecturer
Education
January 1989 - August 1996
University of Wyoming
Field of study
  • Astronomy and Astrophysics

Publications

Publications (310)
Article
Sediment budgets are fundamentally important for planetary science. However, only one primary method, based on remote sensing, is currently available for determining extraterrestrial sediment budgets. For determining sediment budgets on Earth, both in-situ and remote sensing methods are available. Despite the widespread use of the two methods, ther...
Article
Nearly half a century ago, two papers postulated the likelihood of lunar lava tube caves using mathematical models. Today, armed with an array of orbiting and fly-by satellites and survey instrumentation, we have now acquired cave data across our solar system—including the identification of potential cave entrances on the Moon, Mars, and at least n...
Article
Full-text available
Thermal response of the surface to solar insolation is a function of the topography and the thermal physical characteristics of the landscape, which include bulk density, heat capacity, thermal conductivity and surface albedo and emissivity. Thermal imaging is routinely used to constrain thermal physical properties by characterizing or modeling cha...
Article
Mars Polar Science is a subfield of Mars science that encompasses all studies of the cryosphere of Mars and its interaction with the Martian environment. Every 4 yr, the community of scientists dedicated to this subfield meets to discuss new findings and debate open issues in the International Conference on Mars Polar Science and Exploration (ICMPS...
Article
Full-text available
Since the initial experiments nearly 50 years ago, techniques for detecting caves using airborne and spacecraft acquired thermal imagery have improved markedly. These advances are largely due to a combination of higher instrument sensitivity, modern computing systems, and processor intensive analytical techniques. Through applying these advancement...
Research
As part of a NASA-funded study of diurnal thermal imaging at a Mars analog site, we conducted simultaneous oblique thermal imaging and in situ temperature measurements within two regions of interest on the Pisgah lava field, near Ludlow, California. Both regions of interest contained either cave or cave-like alcoves. Data released in this report wa...
Preprint
Full-text available
Martian subsurface habitability and astrobiology can be evaluated via a lava tube cave, without drilling. MACIE addresses two key goals of the Decadal Survey (2013-2022) and three MEPAG goals. New advances in robotic architectures, autonomous navigation, target sample selection, and analysis will enable MACIE to explore the Martian subsurface.
Article
In the icy beds of its polar layered deposits (PLD), Mars likely possesses a record of its recent climate history, analogous to terrestrial ice sheets that contain records of Earth's past climate. Both northern and southern PLDs store information on the climatic and atmospheric state during the deposition of each layer (WPs: Becerra et al.; Smith e...
Article
Mars Polar Science is an integrated, compelling system that serves as a nearby analogue to numerous other planets, supports human exploration, and habitability. Mars possesses the closest and most easily accessible layered ice deposits outside of Earth, and accessing those layers to read the climate record would be a triumph for planetary science.
Article
Full-text available
Mars Polar Science is an integrated, compelling system that serves as a nearby analogue to numerous other planets, supports human exploration, and habitability. Mars possesses the closest and most easily accessible layered ice deposits outside of Earth, and accessing those layers to read the climate record would be a triumph for planetary science.
Article
Extensive evidence of landform-scale martian geomorphic changes has been acquired in the last decade, and the number and range of examples of surface activity have increased as more high-resolution imagery has been acquired. Within the present-day Mars climate, wind and frost/ice are the dominant drivers, resulting in large avalanches of material d...
Poster
Full-text available
Caves often support sensitive animal populations ranging from bats to subterranean-adapted invertebrates, salamanders, and fishes. Developing a framework to detect caves using GIS and remote sensing could serve as an invaluable conservation tool. Researchers could systematic identify caves on the landscape, prioritize caves for biological survey du...
Conference Paper
Full-text available
MACIE, a potential New Frontiers class mission concept named after Macie Roberts one of NASA’s human computers, will address two science goals: 1) Have habitable conditions ever existed within Martian lava tubes? And 2) did life emerge or seek refuge in Martian lava tubes? We are currently evaluating the instrument and architecture trade space usin...
Preprint
We propose a simplified process to advance martian speleology from a rudimentary understanding to acquiring the data required to evaluate and select the best candidates for astrobiological investigations and human outposts.
Conference Paper
Full-text available
We propose a simplified process to advance martian speleology from a rudimentary understanding to acquiring the data required to evaluate and select the best candidates for astrobiological investigations and human outposts.
Conference Paper
Full-text available
Caves represent one of the best localities for finding evidence of life beyond Earth. We assessed the potential science returns for a New Frontiers Mars lava tube (cave) exploration mission. The Mars Astrobiological Caves and Internal habitability Explorer (MACIE) would address a key recommendation of the 2019 National Academies’ Astrobiology Strat...
Conference Paper
Full-text available
Windblown sand dunes are one of many distinct aeolian features that have shaped the martian landscape. Many important questions about the large dark dunes remain unanswered, such as: To what extent does aeolian sand composition represent the surrounding surface? What is the provenance of dune sand and how did it form into wind-mobilized grains? How...
Article
The Fifth International Planetary Dunes Workshop: From the Bottom of the Oceans to the Outer Limits of the Solar System; St. George, Utah, 16–19 May 2017
Article
Full-text available
Infrasonic resonance has previously been measured in terrestrial caves by other researchers, where Helmholtz resonance has been suggested as the plausible mechanism resulting in periodic wind reversals within cave entrances. We extend this reasoning to possible Martian caves, where we examine the characteristics of four atypical pit craters (APCs)...
Article
We provide a historical context of the International Conference on Mars Polar Science and Exploration and summarize the proceedings from the 6th iteration of this meeting. In particular, we identify five key Mars polar science questions based primarily on presentations and discussion at the conference and discuss the overlap between some of those q...
Article
Dunes on Venus, first discovered with Magellan Synthetic Aperture Radar (SAR) in the early 1990s, have fueled discussions about the viability of Venusian dunes and aeolian grain transport. Confined to two locations on Venus, the existence of the interpreted dunes provides evidence that there could be transportable material being mobilized into aeol...
Article
Full-text available
We present a concept for using a polarization sensitive multispectral lidar to map the seasonal distribution and exchange of volatiles among the reservoirs of the Martian surface and atmosphere. The LIDAR instrument will be a multi-wavelength, altitude-resolved, active near-infrared (NIR, with 10 bands around 1.6 microns) instrument to measure the...
Article
The composition of two dune fields, Ogygis Undae and the NE–SW trending dune field in Gale crater (the “Bagnold Dune Field” and “Western Dune Field”), were analyzed using thermal emission spectra from the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) and the Mars Odyssey Thermal Emission Imaging System (THEMIS). The Gale crater dun...
Article
2nd International Planetary Caves Conference; Flagstaff, Arizona, 20–23 October 2015 https://eos.org/meeting-reports/planetary-caves-role-in-astronaut-bases-and-the-search-for-life
Conference Paper
Full-text available
Introduction: Since Rinker’s [1] groundbreaking work on terrestrial cave detection nearly 50 years ago, our ability to find caves using airborne and spacecraft acquired imagery has improved considerably. Due to superior analytical techniques, improved instrument optics, and high resolution imagery, we have furthered terrestrial cave detection capab...
Article
Full-text available
Scientists observe aeolian bed forms, or dune-like structures, throughout the solar system in a range of locations, from bodies with only transient atmospheres, such as comets, to places with thick atmospheres, such as Venus and the Earth’s ocean floor. Determining the source of sand and the different dune formations that result are thus important...
Article
Small-scale variations of seasonal ice are explored at different geomorphic units on the Northern Polar Seasonal Cap (NPSC). We use seasonal rock shadow measurements, combined with visible and thermal observations, to calculate density over time. The coupling of volume density and albedo allows us to determine the microphysical state of the seasona...
Article
A clarification for the enumeration of Mars years prior to 1955 is presented, along with a table providing the Julian Dates associated with Ls = 0° for Mars years −183 (beginning of the telescopic study of Mars) to 100. A practical algorithm for computing Ls as a function of the Julian Date is provided. No new science results are presented.
Article
More than 100 pit craters in the Tharsis region of Mars exhibit morphologies, diameters, and thermal behaviors that diverge from the much larger bowl-shaped pit craters that occur in most regions across Mars. These Atypical Pit Craters (APCs) generally have sharp and distinct rims, vertical or overhanging walls that extend down to their floors, sur...
Article
This paper will constrain the possible sources and processes for the formation of recently observed H2O vapor plumes above the surface of the dwarf planet Ceres. Two hypotheses have been proposed: (1) cryovolcanism where the water source is the mantle and the heating source is still unknown or (2) comet-like sublimation where near-surface water ice...
Article
Remote sensing data acquired during Dawn’s orbital mission at Vesta showed several local concentrations of high-albedo (bright) and low-albedo (dark) material units, in addition to spectrally distinct meteorite impact ejecta. The thermal behavior of such areas seen at local scale (1–10 km) is related to physical properties that can provide informat...
Conference Paper
Full-text available
We study surface features, albedos, and densities of seasonal CO2 ice over time on the north pole of Mars. Our results suggest two distinct endmembers. We develop a conceptual model to explain the changes in the states of these ices during spring.
Article
The spectral signature of water ice was observed on Martian south polar cap in 2004 by the Observatoire pour l'Mineralogie, l'Eau les Glaces et l'Activite (OMEGA) (Bibring et al., 2004). Three years later, the OMEGA instrument was used to discover water ice deposited during southern summer on the polar cap (Langevin et al., 2007). However, temporal...
Conference Paper
Full-text available
Introduction: Dune fields are abundant on the Martian surface, and their mineralogical composition can reveal much about their origin and history, as well as planetary processes. Here, we use Mars Global Surveyor Thermal Emission Spectrometer (TES) [1] data to examine multiple Orbital Counter Keeper (OCK) observations over two dune fields. Only one...
Article
We present the scientific case to build a multiple-wavelength, active, near-infrared (NIR) instrument to measure the reflected intensity and polarization characteristics of backscattered radiation from planetary surfaces and atmospheres. We focus on the ability of such an instrument to enhance, perhaps revolutionize, our understanding of climate, v...
Article
first ever regional thermal properties map of Vesta has been derived from the temperatures retrieved by infrared data by the mission Dawn. The low average value of thermal inertia, 30 ± 10 J m-2 s-0.5 K-1, indicates a surface covered by a fine regolith. A range of thermal inertia values suggesting terrains with different physical properties has bee...
Article
Full-text available
Including ISIS support will strengthen most instrument or mission proposals.
Article
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We focus on the advance and retreat of the Mars seasonal polar cap edges between Mars Years 24-28. We compare results from TES to MOC and OMEGA images.
Article
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We highlight the need to restart NASA planetary cartography planning, a foundation of planetary science and exploration.
Article
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Vesta’s surface temperatures are compared to thermal models. Regions where H2O ice may be stable are identified, along with areas that may be dust-free.
Article
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Elemental mapping by Dawn’s gamma ray and neutron detector reveals the colorful chemistry of Vesta’s howarditic regolith.
Article
Pitted terrains have been found on Vesta, where they are seen as regions with high thermal inertia. We present a detailed analysis of the thermophysical characteristics of this kind of terrains.
Article
Global maps of the macroscopic thermal neutron absorption cross section of Vesta's regolith by the Gamma Ray and Neutron Detector (GRaND) on board the NASA Dawn spacecraft provide constraints on the abundance and distribution of Fe, Ca, Al, Mg, and other rock-forming elements. From a circular, polar low-altitude mapping orbit, GRaND sampled the reg...
Article
Olivine-rich deposits were discovered locally on Vesta's surface. Unexpectedly, these deposits occur far away from the prominent Rheasilvia basin: they were rather found in the northern hemisphere as a layer exposed in walls and in ejecta of two craters, scattered more diffusely over a broad area [1]. Furthermore, while diogenite was firmly identif...
Conference Paper
Full-text available
Density of seasonal CO2 ice was analyzed at the Phoenix Landing Site in MY 29. We propose that the ice begins as snow, anneals into slab, and then fractures.
Article
The Third International Planetary Dunes Workshop took place in Flagstaff, AZ, USA during June 12–15, 2012. This meeting brought together a diverse group of researchers to discuss recent advances in terrestrial and planetary research on aeolian bedforms. The workshop included two and a half days of oral and poster presentations, as well as one forma...
Article
Full-text available
We discuss global distribution of dune fields and discuss global wind directions, as derived from dune centroid azimuth and slipface orientations.
Article
We present temperature maps and spectra of pitted terrain observed by the VIR experiment onboard Dawn, which constrain their composition and physical structure.
Conference Paper
Full-text available
In our study on mineral percentage conformity of the martian dune site, we evaluated Thermal Emission Spectrometer data and studied our analysis technique.
Article
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The new support process and future vision for the USGS ISIS package is discussed.
Article
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In this analysis, we attempted to remove many of the surface physical properties that influence variations in thermal emission and to quantify thermal inertia.