NAI Director's Seminar Series feat. Raymond Pierrehumbert

Event Details

NAI Director's Seminar Series feat. Raymond Pierrehumbert

Time: October 28, 2013 from 11am to 12pm
Location: Adobe Connect
Website or Map: https://astrobiology.nasa.gov…
Event Type: virtual, seminar
Organized By: Mike Toillion
Latest Activity: Oct 24, 2013

Export to Outlook or iCal (.ics)

Event Description

The Puzzle of Low-Density Super-Earths

Presenter: Raymond Pierrehumbert, University of Chicago
When: October 28, 2013 11AM PDT

The dawning era of exoplanet exploration has yielded up many surprises in the form of classes of planets that have no counterpart in our own Solar System. In this talk, I will discuss a class that I refer to as “gas midgets,” which consist of planets in the Super-Earth range of masses or radii, but which have densities so low that most of the planet’s mass must be in the form of volatiles. The poster-child for this class of planets, and the first such to be discovered, is GJ1214b, with a mass of 6.55 Earth masses, a radius of 2.678 Earth radii and a density of only 1870 kilograms per cubic meter. It turns out that GJ1214b is not alone, and a number of other planets in its class have been discovered. Some of these could have hydrogen-rich envelopes, but this model has been essentially ruled out for GJ1214b, for which transit-depth observations point towards a composition with higher molecular weight. The conventional picture of this planet consists of a water-world, but based on work by James Lloyd and myself I will put the case for a carbon-rich planet whose composition is dominated by carbon dioxide surrounding a silicate core.

Many gas midgets are not good candidates for habitability in the conventional sense, but they do provide a valuable check on theories of photoevaporation and atmospheric escape. This is important because the main threat to habitability of planets orbiting M-stars is loss of atmosphere due to the high extreme ultraviolet flux expected for such stars, at least in their youth; were it not for the risk of atmospheric escape, M-star systems would provide the most widespread and stable liquid water habitat in the Universe. There is one class of gas midgets, however, discussed by Eric Gaidos and myself, which not only are potentially habitable but in fact expand the habitable zone to distances far beyond the limits traditionally imposed by carbon dioxide condensation. These are the planets whose density may be explained by a model consisting of a silicate core surrounded by a thick hydrogen atmosphere. The existence of gas midgets in quite close orbits confirms the potential for such atmospheres to be retained. Confirmation by spectroscopic observations that some gas midgets do indeed have a hydrogen envelope would provide support for the existence of this new class of habitable worlds. I will discuss the kinds of biogeochemical cycles that might exist on such worlds, and raise the question of whether their habitability could survive the emergence of life.

Comment Wall

Comment

RSVP for NAI Director's Seminar Series feat. Raymond Pierrehumbert to add comments!

Join SAGANet

Attending (5)

Might attend (3)

Photos

  • Add Photos
  • View All

Blog Posts

Using tried and tested methods of constructing habitats from ethnobotanical and ethnozoological useful species for self sustainability on Mars

Posted by Andrew Planet on June 26, 2020 at 8:00am 0 Comments

To maximize crop yields on Mars it would be advantageous to do away with annuals and biannuals by engineering the latter into perennials as standard. Not only would that entail far less work to grow produce as the act of replanting is made obsolete, but per given cultivated area perennials bring forth more food and materials with less demand from the soil than the equivalent of annuals.

Imagine a superfood annual such as lentils engineered into a lentil tree for which there already…

Continue

Free astrobiology webinars for kids, summer 2020

Posted by Julia Brodsky on June 13, 2020 at 12:28pm 0 Comments

This summer, Art of Inquiry hosts free space exploration and astrobiology webinars for middle-school students and their families all over the world.



Here is a list of what was covered so far, as well as an updated schedule of webinars:

The search for life in the Universe, Dr. Alex Tsapin, JPL (retired)

The history of SETI, SETIQuest editor, Larry…

Continue

Radiolysis-powered life

Posted by Andrew Planet on June 11, 2020 at 9:56pm 7 Comments

This paper greatly extends the possibility of what a Goldilocks zone can be.  Its no longer the Goldilocks zone as a single expanse, its the Goldilocks zones for a particular area

https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2016.0459

¿Are the Venusian sulphuric acid clouds the by product of long dead anoxogenic photosynthetic organisms?

Posted by Andrew Planet on May 4, 2020 at 2:51pm 2 Comments

I just read the piece at the link below entitled "Study: Life might survive, and thrive, in a hydrogen world."

I'd been thinking on similar lines recently, on different atmospheres with early life, but I was considering anoxogenic bacteria whose byproduct is sulfur instead of molecular oxygen. ¿Had life evolved on Venus could its sulfuric clouds be the signature byproduct of such life with no branches ever evolving to produce the equivalent of Earth's Great…

Continue

Videos

  • Add Videos
  • View All

Forum

Ask your questions here!

Started by Gina Riggio in SAGANet Discussions. Last reply by Pritha Jaipal yesterday. 127 Replies

If you are trying to ask a question live during Ask an Astrobiologist, please do so in the main chatroom at the bottom of the screen! You can also ask on twitter…Continue

Inhabitation on mars, with plants or without?

Started by Chirag Parmar in The Cutting-Edge of Astrobiology. Last reply by Chirag Parmar on Monday. 2 Replies

hello there, Chirag Parmar this side!i am a biotechnology student and currently on research of plants on other planets! The main issue is the gravity of the planet! If we take mars as an example, the…Continue

Tags: #plantsonplanets, #mars, #plants

Have we been looking in the wrong time-frame? Requesting feedback on a recent paper.

Started by Christopher J Reiss in The Cutting-Edge of Astrobiology. Last reply by Greg Bowen Jun 30. 5 Replies

Let me first say Hi to everyone as a new member here!   I hope you are all safe, sound, and not too stir-crazy during this Pandemic.I recently stumbled upon a notion for SETI which seems so simple I…Continue

Interactive Online Astrobiology for 10-12 yr olds

Started by Julia Brodsky in Education and Public Outreach Mar 9. 0 Replies

If your 10-12 yr old child is interested in space science, I would like to invite them to our courses. I am a former science teacher,  mom of three, and a former NASA astronaut instructor. I also…Continue

Tags: school, education, middle, astrobiology, STEM

© 2020   Blue Marble Space, a non-profit organization committed to science and science outreach.   Powered by

Badges  |  Report an Issue  |  Terms of Service