Category: Seminars

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Aomawa Shields, GT Physics Seminar, Sept 21, 2020

Events

Recipe for a Habitable Planet

Prof Aomawa Shields of UC Irvine
Monday, Sept 21 at 3pm Eastern

The discovery of numerous small exoplanets has brought the search for life beyond the Solar System into sharp focus on many potentially habitable worlds where life may exist. However, many factors 
and processes can affect planetary climate and habitability, most of which are currently unconstrained by observations, and their effects must be understood to accurately determine a planet’s habitability potential and prioritize planets for observational follow-up. Professor Shields will describe the methods used by her research group to quantify the effects on planetary climate of a range of factors important for planetary habitability, and share recent results from this work, which demonstrates how the unique interactions between a star and a planet’s atmosphere and surface can produce either a recipe of successful ingredients for habitable surface conditions, or one that reveals less favorable planetary prospects for life.

Seminar details here.

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PSAS: Andrew Mullen: Microscopes for Earth and Space Exploration

Events

A microscope for life detection is a top candidate instrument for ocean world and other planetary missions. Microscopes developed for ocean, earth, and space exploration have significant overlap; with analog terrestrial environments offering excellent settings to test techniques potential for space application.

In this talk I will introduce basic principles of microscopic imaging and discuss the application of microscopes for life detection and environmental exploration. I will then present several different microscopic imaging systems developed for both oceanographic exploration and planetary missions. This will include details on a submersible digital holographic microscope (DHM) being developed for the underwater robot Icefin, results from benthic underwater microscopes used to observe seafloor organisms, and towed systems for imaging plankton. At then end of this talk I hope you will have a better understanding of the capabilities of microscopes, their history of use in space and ocean applications, and future potential.

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M. Khademian – Virtual Seminar – May 8

ExplOrigins & Astrobiology Primer Community Review

Speaker: Maryam Khademian

Affiliation: University of Illinois, Department of Microbiology

Date: Friday, May 8, 2020 – 10:00am

Location: BlueJeans

Host: ExplOrigins Group

Title: Oxidative Stress in Anoxic Habitats

Abstract: Bacteroides thetaiotaomicron was examined to determine whether its obligate anaerobiosis is imposed by endogenous reactive oxygen species or by molecular oxygen itself. Previous analyses established that aerated B. thetaiotaomicron loses some enzyme activities due to a high rate of endogenous superoxide formation. However, the present study establishes that another key step in central metabolism is poisoned by molecular oxygen itself. Pyruvate dissimilation was shown to depend upon two enzymes, pyruvate:formate lyase (PFL) and pyruvate:ferredoxin oxidoreductase (PFOR), that lose activity upon aeration. PFL is a glycyl-radical enzyme whose vulnerability to oxygen is already understood. The rate of PFOR damage was unaffected by the level of superoxide or peroxide, showing that molecular oxygen itself is the culprit. The cell cannot repair PFOR, which amplifies the impact of damage. The rates of PFOR and fumarase inactivation are similar, suggesting that superoxide dismutase is calibrated so the oxygen- and superoxide-sensitive enzymes are equally sensitive to aeration. The physiological purpose of PFL and PFOR is to degrade pyruvate without disrupting the redox balance, and they do so using catalytic mechanisms that are intrinsically vulnerable to oxygen. In this way the anaerobic excellence and oxygen sensitivity of B. thetaiotaomicron are two sides of the same coin.