Welcome to the VPL Spectral Academy! This page provides a version of the VPL Spectral Explorer intended for use in an academic learning environment. Use the lesson plan just below the interactive visualization for a series of exercises originally developed for the 2018 Cloud Academy. See the Tutorial page more information on how to use the interactive Spectral Explorer.
HABITABILITY, BIOSIGNATURES AND CLOUDS – INTERACTIVE LESSON
Created by V. Meadows and J. Lustig-Yaeger (2018)
In this lesson we will explore simulated terrestrial exoplanet spectra to better understand how clouds impact planetary spectra, and explore some of the challenges posed by clouds for the characterization of exoplanet atmospheres.
The VPL Spectral Explorer has two main interactive components: a plot window at the top and a table of planetary spectral models at the bottom. Spectral models selected in the table at the bottom are displayed in the plot at the top. The table is organized into columns of “Star”, “Planet”, “Description”, “Meta”, which typically contain key information on each spectrum going from the broad system to details on the atmospheric composition. Multiple spectra can be selected for plotting at the same time by holding the “command” key (on a Mac) or the “control” key (on a Linux or PC), or by selecting an entire category in the table (e.g. “Archean Sun” in the “Star” column).
The Spectral Explorer has a variety of additional options. Users can select between “Direct” and “Transmission” spectrum types using option boxes in the upper left corner of the window. Note that when switching between spectrum types, users must re-select items in the table, even if they appear selected. Users can use the “Molecular Band Overlay” dropdown menu at the top of the window to draw vertical lines at the wavelengths corresponding to major molecular absorption bands for the selected molecule. The wavelength range of the plot can be adjusted using the sliders (or by inputting values into the boxes) at the top right of the window.
Use the VPL Spectra Explorer to perform the following 4 Explorations:
Exploration 1
Display the two transmission spectra for “Pandora b”. Use the Molecule overlay function to identify molecules in these spectra. One of these spectra contains clouds. Which one is it? What is the evidence for clouds in this spectrum? Discuss whether this planet is likely to be habitable or not. What evidence is there in the cloudy spectrum that the planet is habitable?
Then display the direct imaging spectra for Pandora b. Identify molecules in the spectrum. Do these spectra change your conclusions about the nature of Pandora b? Why or why not?
Exploration 2
Display both the transmission and direct spectra for Pandora c. Use the molecule overlay function to identify molecules in these spectra. Identify which spectrum has a haze.
Now display the spectra for Pandora g. Several of these spectra have hazes in them, and several have clouds. Again, use both the transmission and direct spectra, and your results for Pandora c to identify which spectra have a haze, a cloud, neither, or both. Is the albedo spectrum or the transmission spectrum more sensitive to the differences between each spectrum? Which molecules appear in the spectra? Are they more or less detectable with the clouds/hazes? Does this hold for both transmission and reflected light?
Exploration 3
Display the two transmission spectra for Pandora b (same as Exploration 1), and the transmission spectrum for Pandora d (Modern Earth). Try to place Pandora d within the context of the previously discussed Pandora b spectra (Is Pandora d more similar to Pandora b1 or b2?). Does Pandora d have a cloud? Does it have water features? Is it likely to be habitable? What is the cause of the continuum absorbing radius?
Now plot the same three spectra (b1, b2, and d1) in reflected light, and reassess your answers above. Discuss what other physical mechanisms may be causing the discrepancy.
Exploration 4
Display Pandora e1 and Pandora f1. Can you identify any molecules in the spectra? Are there common molecules? Are there molecules that are unique to one spectrum? Are these the same type of planet, or different planets? Discuss.
Display Pandora h1 and Pandora h2. What is the primary constituent of this atmosphere? What type of planet might this be? Identify the planet with aerosols. Describe the process(es) that might have produced these aerosols.