Wrapping up at JPL

I can hardly believe it, but my internship is officially complete! I am spending my final day in southern California writing this entry. My work at JPL ended on good notes across the board. I gave a fifteen minute presentation of the work I had done over the summer to the other interns and to the scientists/post docs in our lab group. The presentation went very well. I also submitted a final report to Caltech detailing my accomplishments over the summer. The final step now is to put the finishing touches on my manuscript and publish the results! This will be my first publication, and I’m very excited about it. As these results aren’t published yet, I should not discuss them here yet. I will add another post in the future when I can do that. For now, suffice it to say that the results will be useful to astronomers and planetary scientists trying to understand the atmosphere of Titan. Moreover, my work makes suggestions as to future work and new project ideas that can be investigated in the future. My hope is to address those next summer at JPL!

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Some thoughts on Titan: My work this summer has offered me the opportunity to develop a strong interest in Titan, one of Saturn’s most interesting moons. Recall that my work has been focusing on understanding some of the molecules that we expect to be found in Titan’s atmosphere, but in tightly controlled laboratory settings, for the purpose of characterization of those molecules.

Titan is a truly amazing place. 50% percent larger than Earth’s moon and 80% more massive, it is the only moon we know of in the solar system with a substantial atmosphere. And substantial is perhaps an understatement! On the surface of Titan, the atmospheric pressure is approximately 150% of the surface air pressure on Earth. The vast majority of that comes from molecular nitrogen (N2), but a good chunk also comes from methane (CH4). Methane is one of the primary constituents of natural gas.

Methane (CH4), a nice, symmetric molecule. The central black atom is the lone carbon atom, and the four blue atoms forming the corners of a tetrahedron are hydrogen.

At the surface of Titan, the 1.5 Earth atmospheres of pressure and the cold temperature (98.29 K = −179 °C = −290 °F) allow methane to exist both in liquid and gaseous form. In fact, methane is to Titan what water is to Earth. There are lakes and rivers of methane, and even methane rain as well. Take a moment to appreciate just how truly bizarre this is: an entire world with weather and surface liquid bodies dominated by the molecules in natural gas.

Less than one month ago, NASA officially announced the we are returning to Titan! The mission is called Dragonfly, and it is pretty incredible:

Dragonfly will launch in 2026 and arrive at Titan in 2034. The eight year voyage is a testament to the impressive distance between Earth and Saturn, around 9 AU (astronomical units, i.e. the average distance from Earth to the Sun), or well over one billion kilometers. Dragonfly will land a rotorcraft (think drone!) on Titan’s surface, which will subsequently make a series of ‘leap frog flights’, some as long as several kilometers, to reach areas of interest and collect samples. In terms of the science that Dragonfly will engage in, I have itemized some of the objectives here:

• Use a mass spectrometer to sample surface material, identifying chemicals relevant to the production of biologically interesting compounds.

• Employ meteorology sensors and remote-sensing instruments to monitor atmospheric conditions.

• Characterization of geologic features using remote-sensing instruments.

• Employ a seismometer to measure subsurface activity and structure.

• While in flight, Dragonfly will also obtain atmospheric profiles, including diurnal and spatial variations.

  • Source: Dragonfly: Exploring Titan's Prebiotic Organic Chemistry and Habitability (PDF). E. P. Turtle, J. W. Barnes, M. G. Trainer, R. D. Lorenz, S. M. MacKenzie, K. E. Hibbard, D. Adams, P. Bedini, J. W. Langelaan, K. Zacny, and the Dragonfly Team. Lunar and Planetary Science Conference 2017.

Pretty neat, right? Allow me to reiterate now perhaps the most important thing we know about Titan: it likely resembles the early, prebiotic Earth (See Clarke DW, Ferris JP. Chemical evolution on Titan: Comparisons to the prebiotic Earth. Orig Life Evol Biosph 1997;27:225-48). For this reason, studying Titan now can potentially help us learn about the early stages of the development of Earth. It is perhaps even possible that studying the chemical interactions on Titan may inform our understanding as to the origin of life itself…

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Finally, I’ll briefly describe the fun day I had yesterday. I visited Mount Wilson Observatory, an historic observatory high up in the nearby mountains with approximately fifteen telescopes, currently. While there are hiking trails to get up there, they’re quite difficult (16 miles round trip…), and I didn’t bring all of my gear out to Southern California with me. I’m intending to do that next summer though! So, instead, I rented a car and drove up. The view from the top is pretty incredible.

Mount Wilson is home to two particularly important instruments in the history of astronomy and astrophysics. First built was the 60 inch reflector of 1908. The world’s largest telescope at the time, this instrument was used to prove that the sun (and therefore the solar system) was actually nowhere near the center of the galaxy, and is instead located approximately halfway out from the center.

The dome housing the 60 inch reflector at Mount Wilson.

The 60 inch instrument itself. Note the electric plugs on the front for scale.

Less than ten years later in 1917, the famous 100 inch telescope was constructed. This was the instrument that Edwin Hubble used to measure the velocities of galaxies, determining that the universe was in fact expanding!

Standing in front of the dome which houses the 100 inch telescope. Due to my terrible photography skills, this picture really betrays the true size of the dome, which is deceptively far away from me in the picture. If you look closely, you can see one of the members of my tour standing near the dome, for scale.

The preposterously large 100 inch telescope, the biggest telescope in the world from 1917 to 1949.

It’s worth taking a moment to appreciate the magnitude of Hubble’s primary discovery with this instrument. Imagine, one of the only things you’re “sure of” in physics is that gravity is attractive; stuff pulls on other stuff. So, when you look out into the universe, you expect to see things generally contracting, approaching one another. Hubble does the experiment, and finds just the opposite. Later in the century, even more bizarrely, it was discovered that not only is the universe expanding (i.e. essentially all galaxies are moving away from all other galaxies) but that expansion is even accelerating, rather than slowing down! This was the first signal of a still not-understood aspect of the universe to which we give the label “dark energy”, a mysterious energy that seems to pervade empty space itself and drive systems further apart from one another on the largest scales.

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My thanks to you for your readership! It has been fun documenting my experience at JPL this summer, and I hope that you’ve gotten something out of it. Apart from a future link to my publication from this work, this will likely be the last post that I do here. I do have some ideas for similar writing projects that I will press on with sometime in the near future. When those materialize, I will make sure you hear about it. :)

Take care,

-Brendan Steffens

After one month at JPL...

Time is flying by! I can hardly believe I’m almost halfway through this experience, which continues to be one of the best of my life. I’m quite certain it is going to be hard to leave this place at the end of the summer…

My appreciation for spectroscopy continues to grow with each day at work. The tremendous wealth of information that these techniques can provide about our universe is simply stunning. As I’ve described in previous posts, it is the quantum mechanical nature of the universe that allows us to glean information about sources of radiation simply by ‘looking at’ at them, regardless of how far away they are. Every element and molecule built out of those elements carries a unique signature of sorts which can be deciphered in the laboratory. This signature changes in subtle ways as a function of the nearby environment (temperature, pressure, etc.), but the fundamental structure of the signature is unchanged. In this sense, methane, for example, ‘looks the same’ in the laboratory as it does in the Earth’s atmosphere, or in the atmosphere of Titan, or even on an exoplanet 63 light years away.

It’s interesting to consider that the universe didn’t need to be this way. We can argue on the metaphysical nuances of a statement like that (indeed, I would very much enjoy that! This isn’t the place though…), but I think the point still stands. I can certainly imagine a universe in which the radiation coming from a source carries much more limited information about the source itself and its environment. Our universe, in contrast, broadcasts information left and right, far and wide. With some committed theoretical and experimental work, we can understand that information and read the secrets of far off places in the universe that we may never get the chance to experience up close. We can even apply spectroscopy to other galaxies that are hundreds of millions if not billions of light years away. It is very fortunate, in my opinion, that we live in a universe that lends itself to being understood in this way, and I believe that pursuit of this understanding leads to progress.

“The more clearly we can focus our attention on the wonders and realities of the universe about us, the less taste we shall have for destruction.” 

Rachel Carson - Marine Biologist

I had a particularly interesting and rewarding interaction with my mentor this week. I was inspecting the spectral data that he had collected for the molecule I am studying, n-butane, and came across an interesting looking feature. Recall that a spectrum looks something like the following:

When we talk about ‘features’ of a spectrum, we’re talking about places where the spectrum is not simply flat, like the large downward spikes you see in the CO2 spectrum above, indicating the frequencies of light that CO2 ‘likes’ to absorb and emit. Anyway, the feature that I was looking at resembled something called a “hotband”. These are associated with transitions between excited states of an atom/molecule, as opposed to transitions between the ground (lowest energy) state and an excited state. Because these features become more active at higher temperatures (hence the name hot band), you can detect them by observing multiple spectra of the same molecule at different temperatures. If a feature is present in warmer spectra and absent in colder spectra, you might be looking at a hotband.

I called my mentor over to confirm this observation, as the concept was still fairly new to me at the time, and I wanted to check my understanding. He inspected the feature that I had plotted for about ten seconds before saying (I paraphrase) ‘Yes, that is a hotband! Now, recognize and appreciate that you are the first human being to see this particular feature of butane.’

He wasn’t exaggerating at all in that statement. These data were collected using a state-of-the-art instrument at extremely high resolution. Every day that I work with this data, I have the privilege of being the first person on the planet to read the geometric and quantum mechanical details of this molecule, the first agent of the universe with access to these impressively fine details. It is for reasons like this that science is so inherently rewarding to me. Every experiment, every observation, every analysis carries with it the possibility of discovery. We can pursue those discoveries purely for the sake of discovery itself, but it is also worth recognizing the benefits (technologies, medicine, etc.) that come along with a refined understanding of the universe.

“Somewhere, something incredible is waiting to be known.”

-Carl Sagan

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That’s enough science for now! Here are some lighter thoughts concerning JPL and my experience.

• The 9/80 schedule at JPL: Full time employees at JPL have the option of what is called a 9/80 schedule. This means that while you still work 80 hours across a two week pay period, you have one Friday off during that time. So, every other Friday is an RDO (regular day off) Friday, allowing for a three day weekend with each paycheck. You make up these hours by working an extra ninth hour on Monday-Thursday of those two weeks. Friday work days are eight hours long. So, every first week of the pay period, you get to go home and start the weekend one hour early, and every second week, you get a three day weekend! I really like this schedule myself, but I can certainly imagine scenarios where the more conventional 8 hours a day, 5 days a week schedule might be more appropriate.

• The nearby riding club: JPL is surrounded by a large horseback riding club. I work in the southernmost building of JPL near some of the stables, so, every day, I get to see riders going out on the trails or practicing dressage. As methane gas is a focal point of the study that takes place in my building, proximity to all of these horses is…..rather interesting.

• Cyclists at JPL: JPL loves cyclists, it seems. There are incentives in place to bike to work, and there are even several tune up stations located around the lab with tools and air pumps. As someone who is very mindful of environmental impact, it is really nice to be acknowledged and taken care of in these ways.

Getting some air into my bike tires at JPL. It was difficult to pry that coffee thermos out of my hands to be able to take this photo.

• Still loving the commute: I’ve commuted by bicycle every day for the past two weeks, and I absolutely love it. It’s about 8 miles of riding, all together. It’s a great way to start the morning and a nice way to finish the work day. It’s a pretty scenic ride, and I’ve only had trash thrown out of a car at me once so far. That’s a pretty good record…

• Weather: I absolutely love the weather in this area. We had a bit of a heat wave recently that lasted two days, with temperatures above 100F. With practically no humidity in the air, though, this feels cooler to me than a typical 80 degree summer day in Florida. Comparing the forecasts for this area and for Florida makes me want to never leave this place. I mean, do I have to?

That’s it for now! Thanks for tuning in. :)

Getting home from JPL

A short video I made of my bike commute home from JPL. Thought I would give everyone a break from the spectroscopy posts.

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

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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).

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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. :)

One week into an internship at NASA's Jet Propulsion Laboratory (JPL)

I am happy to say that I have completed my first week of my internship at JPL! The experience has been tremendously positive so far. JPL is a truly amazing place. The JPL campus consists of approximately 200 different buildings that make up a small “city of scientists and engineers” (they even have their own fire department!), situated at the southern edge of the San Gabriel mountains near Pasadena, California. Here’s a view of the campus from about a mile or two away:

JPL, a city of science on a hill. Photo taken by yours truly.

JPL is a federally-funded research and development center (FFRDC), owned by NASA and managed by California Institute of Technology (Caltech). At any given time, there are six to seven thousand engineers and scientists working here, the majority collaborating on projects related to space exploration. JPL has played a pivotal role in some of the most successful space missions to date, such as the Voyager missions, the Galileo and Cassini missions, and the Mars Science Laboratory (Curiosity rover), just to name a few. If you’d like to see more information about what is currently going on at JPL or what they have accomplished in the past, head on over to their main website, JPL.Nasa.gov.

The atmosphere at JPL is so wonderful. People are there to work on amazing science, and most seem truly thrilled to be doing just that. It’s hard not to be smiling just walking around JPL, because everyone else is! Many parts of the campus are quite beautiful, and some are even scenic, with decent views of the nearby mountains. There are a lot of outdoor spots for lunch, meetings and collaboration, or just grabbing a coffee. There are even several ‘coffee carts’ that serve Starbucks coffee, which is great, because, as my Calculus 1 professor used to say,

Coffee is the lubricant on the gears of science.

—Mark Beintema

“The Mall” at JPL, a popular spot for lunch, coffee, and enjoying the California weather. Photo taken by me.

I will be working in the field of molecular spectroscopy this summer under my mentor, Dr. Keeyoon Sung. We will be measuring the infrared cross sections (explanation to follow) of the n-butane (C4H10) molecule in a variety of temperatures and pressures that are chosen to model the stratosphere of Saturn’s extremely interesting moon, Titan.

Structure of n-butane, a zig-zag chain of carbon atoms, each with a pair or triplet of hydrogen atoms.

Below, you can see an artist’s rendition of the view from the surface of Titan. Hydrocarbons, primarily methane and ethane, play a similar role on Titan as water does here on Earth. A methane lake is seen in this particular image.

Image credit: Original artist unknown, in spite of my best effort to identify him or her…

The goal of my project is to measure the cross section of n-butane as a function of wavelength. The cross section of a molecule is effectively how “big” the molecule is, with respect to incoming radiation. In other words, the larger the cross section of a molecule, the larger the chance that it will “catch” and absorb an incoming photon (particle of light). And again, this is all wavelength (or energy) dependent. The smaller the wavelength of a photon, the larger the energy, and every atom or molecule is very good at absorbing photons of specific energies, and not so good at absorbing photons of other energies. This all arises from the quantum mechanical nature of the universe. Take a look at the spectrum of n-butane below.

The spectrum of n-butane. Image Source: The National Institute of Standards and Technology (NIST) - Chemistry WebBook

If you’ve never seen one of these spectra before, take a moment to understand it, it’s quite straightforward. On the x-axis, we have the wavelength of light. Light is more and more energetic the smaller and smaller the wavelength gets, so on the plot above, the energy of the light being considered decreases as you move further and further to the right. On the y-axis, we are plotting how much of the light of that wavelength, when directed at n-butane, is transmitted, rather than absorbed. A transmittance of 1.0 means full transmission: the light of that particular wavelength passes right through the n-butane, every time. We might say that the molecule is “transparent” to that kind of light. Now, note the sudden dips in the plot at key wavelengths, like the one at wavelength of approximately 3.6 micrometers. It turns out that n-butane is highly absorbing at this (and some other) wavelengths. These wavelengths correspond to specific amounts of energy that n-butane is capable of accepting, so to speak. So, if I aim a photon with wavelength of 3.6 micrometers at a n-butane molecule, there’s a very high chance that the photon will be absorbed by the molecule, “exciting it” and causing some part of it to vibrate and possibly rotate. The type of excitation (i.e. perhaps one of the carbon-carbon bonds begins to stretch in and out repeatedly, or perhaps one of the methyl (CH3) groups on the edge of the molecule begins to rotate) depends on the energy of the absorbed light. The kicker to all this is that every atom and molecule has a unique spectrum, a unique “signature”, of sorts. The form of this signature is governed by quantum mechanics. Through quantum mechanics we can predict the spectra of molecules, and through experimental spectroscopy, we can measure and understand these signatures empirically. Capitalizing on both of these approaches allows us to “decipher” the signature of a molecule to high-precision in the lab, and this allows us to identify the presence of that molecule elsewhere in the universe by simply paying attention to what light is being emitted there.

Understanding the energy-dependent cross sections of n-butane (and other hydrocarbons) is crucial toward making sense of the data that the Cassini mission (and others, like Voyager) have collected from the atmosphere of Titan. These data hint at the presence of butane and other interesting hydrocarbons, but without extremely high-resolution measurements of how these molecules emit radiation in a controlled laboratory setting, it’s difficult to definitively identify them within the Titan atmosphere (and elsewhere). My task will be to analyze the spectrum of butane, calculate the cross sections as functions of wavelength, temperature, and pressure, and publish these results so that astronomers working with the Cassini data to model the Titan atmosphere have a better foundation on which to work.

So, why does knowing the precise details of Titan’s atmospheric makeup really matter? Here are two interesting applications to this sort of work. The first is that Titan, in its present form, may be similar to the Earth back in its early development, long before life evolved (see Clark & Ferris, Chemical evolution on Titan: comparisons to the prebiotic Earth, in Origins of Life and Evolution of Biospheres, 1997). Thus, from a planetary science perspective, understanding the components of Titan’s current atmosphere can inform our understanding of the early development of the Earth as a planetary system. And further, from a biological perspective, understanding Titan’s atmosphere may even shed light on the development of life itself! (see Trainer et al., Organic haze on Titan and the early Earth, Proceedings of the National Academy of Sciences of the United States of America, 2006)

The second application of my work is with regards to future Titan missions. When you land a spacecraft on a planet/moon with an atmosphere, it is crucial to know everything you can about the atmosphere: temperature and pressure profiles, density profiles of each molecular constituent, etc. This allows engineers to make informed decisions when it comes to designing the landing stage, particularly the heat shield and parachutes for the lander, which are crucial in achieving a safe landing. We’ve already landed on Titan once (see image below from the Cassini-Huygens probe), and chances are, we’ll go back again sometime soon!

The surface of Titan as seen by the Huygens probe in 2005.

Anyway, I feel like I have an amazing opportunity on my hands here working at JPL this summer. My plan is to continue to document my experience here on this blog for anyone interested in my work and how I’m spending my time during this summer. My intention is to update once a week, and I’ll do my best to stick to that, most likely updating each weekend. I hope you’ll check back occasionally for more!

Have a question related to this post, or just want to get in touch? Feel free to Contact me.