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<div class="">Hello all,</div>
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<div class="">We are excited to announce that we have a doubleheader* for our planetary seminar next week. <a href="https://aliceboothastronomy.wordpress.com/" class="">Dr. Alice Booth</a> and <a href="https://sites.google.com/umich.edu/jcalahan/home" class="">Dr.
Jenny Calahan</a> will both be joining us from the Harvard CfA | SAO to discuss the astrochemistry of protoplanetary disks. Please join us Tuesday, October 10 @ 12:30 in 54-517 or on Zoom. As always, lunch will be provided (in-person only!) and we encourage
attendees to arrive a bit early to get food.</div>
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<div class="">Alice and Jenny will be on campus all day on Tuesday and are available to meet with members of the community. You can sign up for individual meetings <a href="https://docs.google.com/spreadsheets/d/1OnvmCMDJajrkRsSWai7NNZzyqzxODlpfv--cVfB6kWU/edit?usp=sharing" class="">here</a>.</div>
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<div class="">You can find the talk titles, abstracts, and Zoom information below. We hope to see you there!</div>
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<div class="">-John</div>
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<div class="">* There is also a weekly doubleheader—we have a special planetary seminar on Wednesday October 11 @ 12:00 in 54-1623. More details to follow.</div>
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<div class="">Alice Booth:</div>
<div class=""><i class="">Sublimating ices feeding forming planets</i></div>
<div class="">The chemical conditions in protoplanetary disks determine the composition of planets, moons and comets. In recent years, observations of disks with the Atacama Large Millimetre Array have allowed us to build up a picture of the chemical composition
of disks in 10-100 au scales. The typical disk has an elevated C/O ratio and a lack of oxygen-bearing complex organic molecules, but there are a few interesting exceptions.Transition disks around young intermediate-mass stars uniquely show oxygen-rich chemistry
due to the sublimation of water and organic-rich ices. In this talk, I will share new molecular line observations of such systems and discuss how they give us a window into the typically unobservable planet formation reservoir. </div>
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<div class="">Jenny Calahan:</div>
<div class=""><i class="">Signatures of UV Chemistry in Protoplanetary Disks</i></div>
<div class="">The chemical reservoir within protoplanetary disks has a direct impact on planetary compositions and the potential for life. A long-lived carbon- and nitrogen-rich chemistry at cold temperatures (≤ 50 K) is observed within cold and evolved planet-forming
disks. This is evidenced by bright emission from small organic radicals in 1-10 Myr aged systems that would otherwise have frozen out onto grains within 1 Myr. Using a thermo-chemical modeling framework, I will show how a carbon-rich and UV-rich environment
is necessary to explain observations of CH3CN, HC3N, and HCN towards two of the most well studied and oldest protoplanetary disks we know. This suggests a temporal evolution in the chemical and radiation environment in the planet forming midplane and has wide
impacts on the connections we make between protoplanetary disks and forming planets.</div>
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<div class="">Zoom: <a href="https://mit.zoom.us/j/92448700577" class="">https://mit.zoom.us/j/92448700577</a></div>
<div class="">Pw: 54100</div>
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