Lesson 9: Molecules, Light, and Planets
Key Learning Objectives:
Describe how spectroscopy can be used to find biosignatures in exoplanets from Earth-based space observatories
Understand how to convert from a rainbow visual spectra to a intensity vs wavelength/frequency plot
Identify different molecules within a complicated spectra
In this lesson you'll find...
Identifying biosignatures in exoplanet atmospheres
Graphing the rainbow
Goldilocks and the three planets
Identifying Biosignatures in Exoplanet Atmospheres
We have studied that the interaction of electromagnetic waves with either atoms or molecules (spectroscopy) leads to fingerprints for these entities in the form of a spectrum. We saw that for molecules, those electromagnetic interactions can happen in different ways depending on the kind of electromagnetic radiation with which the molecule is interacting and we realised that infrared spectroscopy is the best option for the identification of molecules in the atmosphere of distant planets.
With the understanding that spectroscopy is a valuable tool for identifying the myriad of molecules considered potential biosignatures in exoplanet atmospheres, the subsequent query arises: How can scientists observe these atmospheres, located thousands of miles away from Earth?
Seeking out there in the Universe has been a constant thought of human kind throughout history. Our curiosity to know what is there, where we cannot go by ourselves yet, has worried humanity and lead to develop alternatives that can help us look further. All this process of thinking, trying and making has ended up with the creation and improvement of telescopes.
A telescope is an instrument that help us either magnify or identify distant objects. Why the distinction between magnifying and identifying? Well, some telescopes are made of an arrangement of lenses that help zoom in into distant objects in order to have a better look. On the other hand, other telescopes identify distant objects not by actually looking at them, but measuring their absorption and emission of electromagnetic radiation (in other words, using spectroscopy).
Telescopes based on spectroscopy can be categorised into the same groups in which electromagnetic radiation is classified, e.g., infrared, microwave telescopes, etc. However, for the seeking of biosignatures in exoplanets, infrared telescopes are used.
Brief explanation of how information is collected from exoplanet atmospheres using space-based infrared telescopes
How does the process work?
Telescopes are built on Earth with all the specifications needed to make them work properly for their purposes. They can either remain on Earth or be launch to orbit around it, depending on the aim for which they've been built.
Once the telescope is all set up to work, it points to an specific region in the Universe and waits to collect enough electromagnetic radiation from a particular object.
Once the data is collected, it is processed in order to have clear spectra.
The spectra are analysed and then the molecules are identify!
Graphing the Rainbow
This activity has been adapted from "Project Spectra!" developed by the University of Colorado Boulder's Laboratory for Atmospheric and Space Physics.
Look at the following examples. Each of the spectra on the left can be displayed as a line plot on the right. The bright colours have high intensities, while the dark lines have low or zero intensity.
Activity
Match the spectra on the left with the corresponding line plot on the right.
Goldilocks and the Three Planets
The following are the infrared spectra for six common molecules. The x-axis in these figures corresponds to the wavelength of the infrared radiation absorbed by the molecule, while the y-xis represents the intensity of each absorption.
Activity
Below are the infrared spectra for Mars, Venus, and Earth, respectively. Identify the molecules present on each of these planets based on the infrared spectra presented above. Be careful of the x-axis scales of each of these plots
