2024 Guest Speaker Schedule

Exploring Ocean Worlds Beyond Earth

DATE	SPEAKER	TOPIC
February 8	Steve Vance NASA Jet Propulsion Laboratory	Spacecraft investigations of ocean world habitability The Galileo and Cassini missions revolutionized our understanding of the outer solar system, revealing numerous confirmed and potential ice-covered ocean moons. The study of ocean worlds still relies on remote observations and extrapolation from conditions on Earth that feed informed speculation about the possibility for life. I will review the next generation of exploring ocean world habitability, represented by the Europa Clipper (Vance et al. 2023). My own research investigates how Europa might support life, and how geophysical measurements might constrain that. I will review possible redox conditions in Europa’s ocean (Vance et al. 2016), and our group’s approach for using laboratory physical and chemical data to explore how different possible Europa interiors might look to Europa Clipper and other future missions (Vance et al. 2018, 2021). Suggested reading
February 15	Tori Hoehler NASA Ames Research Center	Biological Potential and Biosignature Potential of the Ocean Worlds Life as we know it requires liquid water, specific elements, energy, and suitable physicochemical conditions. The last few decades of solar system exploration have revealed that several bodies in our solar system may possess extensive liquid water oceans. Spacecraft observations and theoretical considerations suggest that the elements required by life may be abundant within these oceans. However, lacking direct access to light or to the products of photosynthesis, any life in these oceans may be limited to fluxes of energy that are many orders of magnitude lower than they are on Earth. I will consider the resulting implications for the nature and abundance of evidence for life, using Earth’s oceans as an empirical point of reference.
February 22	NO SPEAKER
February 29	Donna Blackman UC Santa Cruz	Taking (sub)seafloor Earth knowledge out to other Ocean Worlds in our Solar System Half a century of marine geophysical research on Earth forms a strong basis for interpreting the processes that shape our ocean floor and its subseafloor structure. The 'Rocky Interior' component of our Exploring Ocean Worlds collaborative project investigates aspects of knowledge from Earth's (sub)seafloor that can provide insight on other Ocean Worlds (OW) such as Enceladus, Europa, and Titan. This geophysical work is done with broader intent to provide results that can feed into subsequent investigations of geochemical exchange that could have potential to support life. Seafloor heterogeneity had been ignored in planetary studies prior to the ExOW project but on Earth it is a key factor controlling the nature and distribution of subseafloor hydrothermal flow. While many seafloor features are produced by tectonic forces on Earth, mechanisms to create ocean floor topography on OW could also (have) exist(ed). Enhanced thermal gradients associated with kilometer-scale seafloor features host known hydrothermal venting on Earth. Here we explore whether such systems could be physically viable on OW where gravity is just a fraction of Earth's and the structure of the rocky interior could differ notably. We find that the occurence of km-scale relief with sustainable hydrothermal flow cannot be ruled out. While current planetary observations cannot discern whether such seafloor variability and hydrothermal flow occurs, our findings indicate that their presence should still be considered in ongoing modeling of OW processes.
March 7	Laurie Barge NASA Jet Propulsion Lab	Searching for Signs of Life and its Origin on Other Planets Is there life elsewhere in the solar system, and if so how can we find it? Although Earth provides a variety of examples of what biology can look like, examples of the critical steps between abiotic and biotic systems are lacking because the prevalence of life on our planet has erased its record of prebiotic conditions. The distinction between biotic and abiotic is still often unclear in astrobiology, partly because abiotic chemistry can become more complex when devoid of biological influence. Prebiotic chemistry may still be a current or formerly active process on other worlds with detected chemical gradients and organics, for example on ocean worlds such as Enceladus which may host active hydrothermal systems. In this talk I will discuss our group’s work on simulating prebiotic systems that aim to bridge the gap between geochemistry and biochemistry, and how we can use this to aid the search for life and its origin on other planets.
March 14	Justin Lawrence Honeybee Robotics	Diving Deeper with Robotic Platforms for Ocean World Science In our solar system, worlds like Europa and Enceladus have saline, liquid oceans below icy shells. Mars has thick deposits of buried ice and even thicker polar ice caps. These environments could holds signs of past life, be presently habitable, or potentially even be inhabited - but present significant new technical challenges to planetary exploration. How can we access and sample them? What sort of scientific investigations should we focus on? How can we design instrument suites and sampling systems to search for past or present life? In this talk, I’ll survey multidisciplinary efforts from our community of scientists and engineers working on robotic science platforms for future subsurface astrobiology missions.
March 21	Wanying Kang MIT	On icy satellites, size controls the ice geometry Enceladus and Europa, two icy satellites in our solar system, share similar surface temperatures and mean ice thickness. Despite that, their ice shell geometries are likely to be very different. Gravity and shape measurements taken on Enceladus favor a strongly poleward thinning ice shell, whereas Europa’s ice shell seems to be much flatter, supported by its limb profile. This work proposes a mechanism to explain such a difference, which may be generalized to make predictions for other icy satellites. The key behind is the ocean dynamics. Driven by the temperature and salinity gradients underneath a thickness-varying ice shell, overturning circulations and baroclinic eddies will form, redistributing heat and tracers over the globe. The ocean heat transport (OHT) will, in turn, flatten the ice shell through the ice-pump mechanism. The efficiency of the OHT, however, varies with the satellite’s size and rotation period. In this work, we derive scaling laws that govern the OHT amplitude, verify the scalings using numerical simulations, and use them to predict the equilibrium ice thickness variations for icy moons with various sizes and rotation periods. Because of Europa’s strong gravity and slow rotation, its ice thickness variation is predicted to be less than 2km, in contrast to a 12+km ice thickness variation predicted for Enceladus. Given the OHT scaling laws, we demonstrate the possible ice evolution pathways for Enceladus and Europa using an ice evolution model with parameterized OHT.
March 28	SPRING BREAK - NO SPEAKER
April 4	Sam Howell NASA Jet Propulsion Laboratory	Plate Tectonics and the Search for Life Europa's liquid water ocean teases unparalleled potential for extraterrestrial life in our solar system, with a habitability story involving plate tectonics, Jupiter's radiation, and neighboring moons. Launching in October 2024, NASA’s flagship Europa Clipper mission is embarking on a quest to revolutionize our understanding of habitability beyond Earth. This talk will explore the complex, multi-discipline habitability science of Europa, including the unique role of a new style of planetary plate tectonics. Bridging terrestrial plate boundary processes, from seafloor spreading to subduction, with those of the thick ice shell of Europa, I’ll discuss transitioning from the abyssal exploration of the Earth to the distant exploration of an alien ocean.
April 11	Jill Mikucki University of Tennessee	Exploring Earth's Ice to Imagine Extraterrestrial Worlds Earth’s cryosphere, which includes glaciers, icesheets, and permafrost, can inform the exploration of extraterrestrial targets in our solar system. Subglacial environments are the realm of the cryosphere at the base of glaciers and ice sheets that is characterized by permanent darkness, high pressures and low temperatures. This realm is hydrologically diverse, harboring saturated sediments, streams and lakes. Because some subglacial realms are formed by geothermal process or persist as brines, salt or metal stress may also shape the system. In the absence of sunlight, the extremophiles that persist and thrive in subglacial systems must harness energy from chemical reactions and support the manufacture of organics (primary production) via chemosynthesis. In this seminar, we will also discuss how subglacial environments and the microbial communities they host can serve as unique analog features for the testing of space-bound robots and life detection approaches.
April 18	Chris Glein Southwest Research Institute	Is there P in Enceladus's ocean? Enceladus, one of the most alluring moons in the solar system, is of great interest because it has a subsurface water ocean that might be able to support life. In this talk, Dr. Christopher Glein will present a chronicle of habitability from spacecraft exploration of Enceladus, which will culminate with recent modeling and observational results that enabled us to resolve the mystery of phosphorus on this moon of Saturn.
April 25 LOCATION: CARRIAGE HOUSE	Annette Rowe University of Cincinnati	Water, Rocks and Microbes: serpentinization as a natural bioelectrochemical system Electron transfer is an essential process for all life forms. All known forms of biological energy conservation involve taking electrons from one material (i.e., eating) and putting them on another (i.e., breathing). Microorganisms have evolved to use a broad range of electron donors and acceptors, through diverse mechanisms, to accomplish these vital electron transfer reactions. While the microbial ecology of how and when microbes use different electron acceptors is relatively well understood, far less is known about the ecology of how and when microbes use alternate electron donors, especially solid phase minerals. This talk will discuss our investigations into cultivating novel organisms that can perform these poorly understood electron transfer reactions from inorganic substrates including solid phase minerals, other microbes, and conductive materials. I will focus on work we are doing in high PH serpentinizing springs and the implications of this work for thinking about life in the subsurface of our planet, as well as the potential for life elsewhere in our solar system.
May 2	Kevin Hand NASA Jet Propulsion Laboratory	Alien Ocean and the Search for Life in the Depths of Space In this talk I will focus primarily on missions past, present, and future and that could reveal whether or not life exists deep within the ocean worlds of the outer solar system. I will discuss the processes of formulation and implementation of spaceflight missions and the many layers associated with cost, schedule, science, and risk.