On the Edge: Exoplanets with Orbital Periods Shorter Than a Peter Jackson Movie
Brian Jackson, Boise State Univeristy
From wispy gas giants to tiny rocky bodies, exoplanets with orbital periods of several days and less challenge theories of planet formation and evolution. Recent searches have found small rocky planets with orbits reaching almost down to their host stars’ surfaces, including an iron-rich Mars-sized body with an orbital period of only four hours. So close to their host stars that some of them are actively disintegrating, these objects’ origins remain unclear, and even formation models that allow significant migration have trouble accounting for their very short periods. Some are members of multi-planet system and may have been driven inward via secular excitation and tidal damping by their sibling planets. Others may be the fossil cores of former gas giants whose atmospheres were stripped by tides.
In this presentation, I’ll discuss the work of our Short-Period Planets Group (SuPerPiG), focused on finding and understanding this surprising new class of exoplanets. We are sifting data from the reincarnated Kepler Mission, K2, to search for additional short-period planets and have found several new candidates. We are also modeling the tidal decay and disruption of close-in gaseous planets to determine how we could identify their remnants, and preliminary results suggest the cores have a distinctive mass-period relationship that may be apparent in the observed population. Whatever their origins, short-period planets are particularly amenable to discovery and detailed follow-up by ongoing and future surveys, including the TESS mission.
Evolving Perspectives on the Atmosphere and Climate of Mars
Dr. Richard Zurek, JPL
Abstract: The planet Mars has both fascinated and tantalized humankind since the invention of the telescope and now well into the age of exploration from space. The first of three waves of space missions to Mars were flyby spacecraft that returned images of a heavily cratered planet with a thin atmosphere, suggesting Mars was more like the Moon than an older Earth. However, Mariner 9, the first spacecraft to orbit another planet, found vast channel and valley networks carved into its surface, as well as towering volcanoes, suggesting that ancient Mars was once much more Earth-like. Subsequent missions have landed on the planet and new orbiters have probed the planet at ever increasing spatial resolution and spectral coverage. As a result of the latest round of space exploration, Mars is revealed to be a complex, diverse planet— one whose climate has changed dramatically over time from an ancient atmosphere where water was active on its surface to a drier, thinner atmosphere shaped by periodic ice ages, to the present atmosphere where dynamic change continues today.
Dr. Zurek is the Chief Scientist in the Mars Program Office, Project Scientist, MRO.
Exploring Impact Heating of the Early Martian Climate
Kathryn Steakley, NMSU
ABSTRACT: Geological evidence implies that Mars may have had a more warm and wet environment during the late Noachian / early Hesperian era (3.5–3.8 billion years ago), but climate models struggle to reproduce such warm conditions. Prior studies with one-dimensional atmospheric models indicate that the water and energy from impacts could provide enough greenhouse warming to raise temperatures above the freezing point of liquid water for many years. We will use the NASA Ames Research Center Mars GCM to characterize potential atmospheric changes induced by impactors ranging in diameter from 50 m to 100 km on a range of early Mars surface pressure scenarios (10-mbar, 100-mbar, 300-mbar, 1-bar, 2-bar, 3-bar). Our objectives are 1) to examine the temperature behavior of the early Martian climate following impacts and determine if environmental conditions on its surface could support liquid water for extended periods of time, and 2) to quantify precipitation rates and examine rainfall patterns on a simulated early Martian surface following impacts and determine if this mechanism is possibly responsible for the formation of observed river valley networks on Mars. Examining climate conditions after impacts with a GCM will allow us to test a potential mechanism for heating the early Martian atmosphere, constrain the magnitude and temporal duration of these potential heating events, and provide insight regarding the availability of liquid water on early Mars which is relevant to its past habitability.
New Tools for Galactic Archaeology from the Milky Way
Gail Zasowski, John Hopkins University
One of the critical components for understanding galaxy evolution is understanding the Milky Way Galaxy itself — its detailed structure and chemodynamical properties, as well as fundamental stellar physics, which we can only study in great detail locally. This field is currently undergoing a dramatic expansion towards the kinds of large-scale statistical analyses long used by the extragalactic and other communities, thanks in part to an enormous influx of data from space- and ground-based surveys. I will describe the Milky Way and Local Group in the context of general galaxy evolution and highlight some recent developments in Galactic astrophysics that take advantage of these big data sets and analysis techniques. In particular, I will focus on two diverse approaches: one to characterize the distribution and dynamics of the carbon-rich, dusty diffuse ISM, and one to map the resolved bulk stellar properties of the inner disk and bulge. The rapid progress in these areas promises to continue, with the arrival of data sets from missions like SDSS, Gaia, LSST, and WFIRST.
Characterization of Biosignatures within Geologic Samples Analyzed using a Suite of in situ Techniques
Kyle Uckert, NMSU
I investigated the biosignature detection capabilities of several in situ techniques to evaluate their potential to
detect the presence of extant or extinct life on other planetary surfaces. These instruments included: a laser desorption
time-of- flight mass spectrometer (LD-TOF-MS), an acousto-optic tunable filter (AOTF) infrared (IR) point spectrometer, a
laser-induced breakdown spectrometer (LIBS), X-ray diffraction (XRD)/X-ray fluorescence (XRF), and scanning electron
microscopy (SEM)/energy dispersive X-Ray spectroscopy (EDS). I measured the IR reflectance spectra of several speleothems
in caves in situ to detect the presence of biomineralization. Microorganisms (such as those that may exist on other solar
system bodies) mediate redox reactions to obtain energy for growth and reproduction, producing minerals such as
carbonates, metal oxides, and sulfates as waste products. Microbes occasionally become entombed in their mineral
excrement, essentially acting as a nucleation site for further crystal growth. This process produces minerals with a
crystal lattice distinct from geologic precipitation, detectable with IR reflectance spectroscopy. Using a suite of
samples collected from three subterranean environments, along with statistical analyses including principal component
analysis, I measured subsurface biosignatures associated with these biomineralization effects, including the presence of
trace elements, morphological characteristics, organic molecules, and amorphous crystal structures.
I also explored the optimization of a two-step LD-TOF-MS (L2MS) for the detection of organic molecules and other
biosignatures. I focused my efforts on characterizing the L2MS desorption IR laser wavelength dependence on organic
detection sensitivity in an effort to optimize the detection of high mass (≤100 Da) organic peaks. I analyzed samples
with an IR reflectance spectrometer and an L2MS with a tunable desorption IR laser whose wavelength range (2.7 – 3.45
microns) overlaps that of our IR spectrometer (1.6 – 3.6 microns), and discovered a IR resonance enhancement effect. A
correlation between the maximum IR absorption of organic functional group and mineral vibrational transitions – inferred
from the IR spectrum – and the optimal IR laser configuration for organic detection using L2MS indicates that IR
spectroscopy may be used to inform the optimal L2MS IR laser wavelength for organic detection. This work suggests that a
suite of instruments, particularly LD-TOF-MS and AOTF IR spectroscopy, has strong biosignature detection potential on a
future robotic platform for investigations of other planetary surfaces or subsurfaces.
Observations of Solar System Bodies with the VLA and ALMA
Dr. Bryan Butler, NRAO
Observations of solar system bodies at wavelengths from submm to meter wavelengths provide important and unique information about those bodies. Such observations probe to depths unreachable at other wavelengths – typically of order 10-20 wavelengths for bodies with solid surfaces, and as deep as tens of bars for those with thick atmospheres (the giant planets). In the past five years, two instruments have been commissioned which have revolutionized the ability to make very sensitive, high-resolution observations at these wavelengths: the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/Submillimeter Array (ALMA). I will present a discussion of results over the past five years from observations from both the VLA and ALMA. These include observations of the atmospheres of all of the giant planets, the rings of Saturn, and the surfaces of many icy bodies in the outer solar system. I will also present plans for the Next Generation Very Large Array (ngVLA), the next step for millimeter to centimeter wavelength interferometry.
Giant Planet Shielding of the Inner Solar System Revisited: Blending Celestial Mechanics with Advanced Computation
Dr. William Newman, UCLA
The Earth has sustained during the last billion years as many as five catastrophic collisions with asteroids and comets which led to widespread species extinctions. Our own atmosphere was literally blown away 4.5 billion years ago by a collision with a Mars-sized impactor. However, collisions with comets originating in the outer solar system accreted much of the present-day atmosphere. Relatively advanced life on our planet is the beneficiary of a number of impact events during Earth’s history which built our atmosphere without destroying a large fraction of terrestrial life. Using very high precision Monte Carlo integration methods to explore the orbital evolution over hundreds of millions of years followed by the application of celestial mechanical techniques, the presentation will explain directly how Earth was shielded by the combined influence of Jupiter and Saturn, assuring that only 1 in 100,000 potential collisions with the Earth will materialize.
Simulating Planetesimal Formation in the Kuiper Belt and Beyond
Rixin Li, University of Arizona
A critical step in planet formation is to build super-km-sized planetesimals in protoplanetary disks. The origin and demographics of planetesimals are crucial to understanding the Solar System, circumstellar disks, and exoplanets. I will overview the current status of planetesimal formation theory. Specifically, I will present our recent simulations of planetesimal formation by the streaming instability, a mechanism to aerodynamically concentrate pebbles in protoplanetary disks. I will then discuss the connections between our numerical models and recent astronomical observations and Solar System explorations. I will explain why all planetesimals likely formed as binaries.