Week 2 at JPL
“I was born not knowing and have had only a little time to change that here and there.”
Richard P. Feynman
Another phenomenal week at JPL! I continue to have the time of my life at this place. I’ve been studying the universe for six or seven years now, and never have I been so certain of the path on which I walk.
After two years of graduate school, two years of extremely difficult classes mixed with time-consuming (yet deeply rewarding!) teaching obligations, it is such a pleasure to focus on a single, well-defined subset of my research interests for an extended period of time. I feel as though I am learning at a rate that I haven’t experienced before; my team and the environment here at JPL make it easy to do so.
As I described in my last post, my work here is in the field of molecular spectroscopy. Through quantum mechanics, any given molecule has a set of vibrational “modes”, each of which is activated/deactivated by a specific amount of energy. For example, here is one of the vibrational modes of methane (CH4):
Sigma1 vibrational mode of the Methane (CH4) molecule, which has tetrahedral structure. The central gray atom is carbon, while the four outer white atoms are hydrogen.
Source: UCLA Department of Earth, Planetary, and Space Sciences
You can see that this mode consists of symmetric (same direction at the same time) stretching of the C-H bonds. This type of vibration corresponds to a specific amount of energy, or a photon of a specific wavelength (turns out it’s about 3.3μm, or 3.3 millionths of a meter). Other vibrational modes look different and correspond to different amounts of energy, with different wavelengths of light being emitted/absorbed due to that particular vibration. Here’s an example of a different vibrational mode of methane.
The Sigma3 vibrational mode of methane.
Source: UCLA Department of Earth, Planetary, and Space Sciences.
You can see that this is obviously a different type of vibration than the first one, with the hydrogen atoms sort of rocking back and forth. This mode turns out to be lower energy (larger wavelength, approximately 7.3μm). Again, what that means physically is if I shoot a photon of light with wavelength of 7.3 millionths of a meter at a molecule of methane, there is a very high probability that the methane will “accept” and absorb the light, becoming “excited”, and vibrating in the way that you see above. Eventually, it may reemit that photon and return to its lower energy state.
The bottom line is that because each molecule of the universe has a different atomic structure, each molecule has different modes of vibration, each with a characteristic energy that we can study in the lab (my job!). Doing so allows us to understand the full spectrum of the molecule (i.e. which wavelengths of light the molecule likes to absorb/emit and which it does not). Then, we can aim a telescope at a light source even billions of light years away, study the light that the telescope receives, and identify the molecular makeup of the distant object. That is spectroscopy in a nutshell, and it is one of the most powerful tools we have in astronomy. So, now, if someone asks you something along the lines of “How do we know what the stars are made of when we’ve never gone there to sample them directly?”, you can provide the answer: spectroscopy. We look at which wavelengths of light are coming from those stars, and this allows us to identify what molecules are sending that radiation our way.
“One important object of this original spectroscopic investigation of the light of the stars and other celestial bodies, namely to discover whether the same chemical elements as those of our earth are present throughout the universe, was most satisfactorily settled in the affirmative.”
Sir William Huggins, 1909, English astronomer and spectroscopy pioneer
In addition to learning a lot more about the work I am and will be doing this summer, I’ve also had the opportunity to attend some really interesting talks this week. Almost every day at JPL there is at least one if not several talks/seminars/lectures that I am able to attend. It’s amazing to have the opportunity to hear first hand updates about cutting edge research in astronomy, planetary science, and cosmology, or engineering updates to upcoming space missions. I’m not permitted to discuss the vast majority of these talks here, unfortunately, but there is one that I can mention so far, and it has been my favorite! It was a 1 hour talk and Q&A session with European Space Agency (ESA) astronaut Samantha Cristoforetti, who spent almost two hundred days on the International Space Station (ISS). Samantha is a charming, articulate speaker. She speaks Italian, English, German, French, and Russian, and she is currently working on Chinese. Listening to her discuss her experience with the ESA and the ISS was absolutely fascinating. I encourage you to check out some videos of her on YouTube!
This talk was held in the Von Karmen auditorium of the JPL Visitors Center, in which you can see scale model replicas of many of the spacecraft that JPL has worked on or is currently developing.
Scale models of JPL spacecraft. In order of appearance, [1] JUNO (a current mission to Jupiter, 1/5 scale), [2] Voyager (a pair of missions to the outer planets, still ongoing, full scale), [3] Cassini (a mission to the Saturn system, recently terminated, 1/2 scale), [4] Huygens probe (in the glass box, landed on Titan), and finally [5] SWOT (Surface Water and Ocean Topography, launch planned for 2021, will make the first global survey of the Earth's surface water).
I also recently had the opportunity to see the Mission Control Center, which was really neat!
The Deep Space Network mission control center at JPL, where current spacecraft missions are actively managed.
Another awesome project I can show you is the Mars 2020 mission. This is sort of the sequel to the Mars Science Laboratory (i.e. Curiosity Rover). It will launch in 2020, land on the Martian surface, and gather rock and soil samples to be collected by a future mission for return back here to Earth. Below, you can see the lander and heatshield being developed in the Vehicle Assembly Building (VAB).
In my freetime, I’m continuing to explore the Pasadena / Altadena area on foot and on bicycle. It’s such an amazing area, with urban regions, and beautiful suburban residential neighborhoods. Many of the homes in this area have orange or lemon trees growing in their yards. Always in sight here are the San Gabriel mountains to the north (I can see them right now as I type this in the garden of my AirBNB!). Among other things I hope to describe in my next post, I plan to include some photos of this scenic area, as well as a short video of the views I get to see everyday while bicycling to JPL.
Thanks for tuning in! Have a great week. :)