Research

I study ice on other worlds.

Radar and the ice of Europa

  • Radio Glaciology Lab, Stanford Doerr School of Sustainability
  • Advisor: Dustin Schroeder
  • Project leads: Natalie Wolfenbarger, then Annie Cheng
1 to 40 km
how thick Europa's ice shell may be, on top of a global ocean
9 and 60 MHz
the two frequencies of REASON, Europa Clipper's radar
2.5 to 2.8
relative permittivity of the dry silica sand we use for ice (ice is 3.2)
$1,500
about what one of the lab's open-source radar systems costs
  1. Jupiter's moon Europa

    The question

    Europa’s ice shell, somewhere between 1 and 40 km thick, sits on top of a global ocean. NASA’s Europa Clipper will look through it with REASON, a radar that transmits at 9 and 60 MHz. Reading those echoes means knowing what different kinds of ice do to a radar signal.

    NASA Europa Clipper
  2. A radargram: radar echoes from the surface and the bed of an ice sheet, from the Radio Glaciology Lab

    My part is brine

    Pockets of chloride and sulfate brine trapped in the ice are conductive, so they reflect and absorb radar strongly.

  3. A bin of sample supplies in the Radio Glaciology Lab: a bag of sand, copper wire, a funnel and a sieve

    A stand-in for the ice

    In the lab we stand in for the ice with dry silica sand (relative permittivity about 2.5 to 2.8, a little below ice’s 3.2) and for the brine with copper granules and wire at different concentrations and shapes.

  4. The FieldFox vector network analyzer on the lab bench, behind the sample supplies

    The measurement

    I measure each mixture’s complex permittivity with a FieldFox vector network analyzer, using parallel-plate and transmission-line methods, then work out attenuation and reflectivity as the inclusion fraction changes.

    My permittivity script
  5. At the lab bench

    What it shows so far

    In most runs, adding copper raises the sand’s permittivity, and rods standing along the electric field raise it most. Under 3% copper by volume, the change is a few percent, close to the scatter between runs, so the next runs use more copper and a fixed gap between the plates. Loss is the harder half: dry sand absorbs too little for the plates to measure, so real salt water comes next. That bears on one of the big open questions about Europa: whether the shell is conductive or convective, which matters for whether it could support life.

    See it on Europa
  6. A diagram: a water sill deep in the ice shell pushes water up a crack toward the surface, the cold walls freeze it partway, and REASON looks down from above

    Can the water get up?

    Europa’s double ridges may form over water that refreezes inside the shell, the way a double ridge in Greenland formed over a refreezing sill (Culberg, Schroeder and Steinbrügge, 2022). I’m writing a model of the race that decides it. A freezing sill swells and pushes water up a crack, and the crack’s cold walls freeze that water on its way. So far, narrow cracks freeze shut partway up, and wider ones can reach the surface before they seal. Wherever the water stops, it leaves briny ice at a depth REASON can reach, and the brine measurements above say how brightly that ice would echo.

  7. A radar antenna on a cliff over the ocean, from the Radio Glaciology Lab

    Where it's going

    The larger project is a catalog of how each kind of inclusion changes the signal, so that a REASON echo can be read backward into what’s in the ice, including the briny ice a sill leaves where its water stopped. The lab also builds open-source radar systems that cost about $1,500.

    Radio Glaciology LabLab GitHub

Astrophysics research

  • KIPAC, Stanford's Kavli Institute for Particle Astrophysics and Cosmology, 2025
  • Mentor: Maya Beleznay

In 2025 I did astrophysics research at KIPAC, on spectra of two millisecond pulsar binaries, PSR J1036-4353 and PSR J1036-8317, from the SOAR telescope in Chile. I reduced the raw frames in IRAF that year. In 2026 I went back and finished both: Doppler shifts around each orbit, radial velocity curves, and from those the masses of the two neutron stars.

  1. Raw images from SOAR
  2. Bias, flat field, wavelength calibration
  3. Spectra
  4. Doppler shifts around each orbit
  5. Radial velocity curves
  6. Masses
Weighing two pulsarsI taught pulsars at Splash

Deep Field

A planetary science wiki that quizzes me back.

Deep Field is how I’m reading my way into planetary science. Every paper I add becomes a lesson I have to pass: short segments, its key ideas redrawn as my own diagrams, and a question at every step.

Every paper it cites gets a card in the library, and the cards link to each other. That’s where the connections show up. A 2022 paper that explains Europa’s double ridges with a look-alike in Greenland’s ice sheet and a 2026 paper on whether ocean water can climb a crack into Europa’s shallow ice end up asking the same question about water inside the shell. When a paper’s numbers don’t agree with each other, the lesson says so.

It grows with every paper I open. Here’s what’s in it so far.

14
papers taught in full, so far
154
papers they cite, each a card in the library
276
links between cards
9
themes, from Europa's ocean to radar sounding

Read so far

  1. Lada, C. J. (1987). Star formation: from OB associations to protostars. In M. Peimbert & J. Jugaku (Eds.), Star Forming Regions (IAU Symposium 115, pp. 1–18). Dordrecht: Reidel. doi.org/10.1017/S0074180900094766
  2. Marois, C. et al. (2008). Direct imaging of multiple planets orbiting the star HR 8799. Science 322, 1348–1352. Read with Marois, C. et al. (2010). Images of a fourth planet orbiting HR 8799. Nature 468, 1080–1083 (doi:10.1038/nature09684). doi.org/10.1126/science.1166585
  3. Mitri, G., & Showman, A. P. (2008). A model for the temperature-dependence of tidal dissipation in convective plumes on icy satellites: Implications for Europa and Enceladus. Icarus 195(2), 758–764. doi.org/10.1016/j.icarus.2008.01.010
  4. Pinte, C. et al. (2018). Kinematic evidence for an embedded protoplanet in a circumstellar disk. ApJ Letters 860, L13. doi.org/10.3847/2041-8213/aac6dc
  5. Culberg, R., Schroeder, D. M. & Steinbrügge, G. (2022). Double ridge formation over shallow water sills on Jupiter’s moon Europa. Nature Communications 13, 2007. doi.org/10.1038/s41467-022-29458-3
  6. Schlichting, H. E., & Young, E. D. (2022). Chemical equilibrium between cores, mantles, and atmospheres of super-Earths and sub-Neptunes and implications for their compositions, interiors, and evolution. The Planetary Science Journal 3(5), 127. doi.org/10.3847/PSJ/ac68e6
  7. Schroeder, D. M., Wolfenbarger, N. S., Steinbrügge, G. B., Culberg, R., Howell, S. M., Spiers, E., & Styczinski, M. (2024). Constraining the thickness of the conductive portion of Europa’s ice shell using sparse radar echoes. Geophysical Research Letters 51(20), e2024GL110635. doi.org/10.1029/2024GL110635
  8. Brin, A., Lauro, S. E., Cosciotti, B., Turchetti, G., Mattei, E., & Pettinelli, E. (2025). Electromagnetic measurements and modeling of rocky and icy crust simulants to support planetary radar sounder exploration. Journal of Geophysical Research: Planets, 130(6), e2025JE008942. doi.org/10.1029/2025JE008942
  9. Hills, B. H., Young, T. J., Lilien, D. A., Babcock, E., Bienert, N., Blankenship, D., Bradford, J., Brighi, G., Brisbourne, A., Dall, J., Drews, R., Eisen, O., Ershadi, M. R., Gerber, T. A., Holschuh, N., Jansen, D., Jordan, T. M., Karlsson, N. B., Li, J., Martín, C., Matsuoka, K., May, D., Oraschewski, F. M., Paden, J., Rathmann, N. M., Ross, N., Schroeder, D. M., Siegert, M., Siegfried, M. R., Smith, E., & Zeising, O. (2025). Radar polarimetry in glaciology: Theory, measurement techniques, and scientific applications for investigating the anisotropy of ice masses. Reviews of Geophysics 63(4), e2024RG000842. doi.org/10.1029/2024RG000842
  10. Wolfenbarger, N. S., Blankenship, D. D., Young, D. A., Scanlan, K. M., Chivers, C. J., Findlay, D., Steinbrügge, G. B., Chan, K., Grima, C., Soderlund, K. M., & Schroeder, D. M. (2025). Radar characterization of salt layers in Europa’s ice shell as a window into critical ice-ocean exchange processes. Geophysical Research Letters, 52(1), e2024GL109144. doi.org/10.1029/2024GL109144
  11. Cheng, A. H., Schroeder, D. M., Wolfenbarger, N. S., Shaper, R., Seltzer, C., & Hills, B. (2026). Anisotropic melt inclusions as a confounding signal for ice-penetrating radar observations. Geophysical Research Letters 53(5), e2025GL120182. doi.org/10.1029/2025GL120182
  12. Ojha, L., Barik, A., & Buffo, J. (2026). Limited direct fluid exchange between the deep subsurface ocean and the shallow subsurface environment of Europa. Nature Astronomy. doi.org/10.1038/s41550-026-02918-2
  13. Schroeder, D. M., Byrne, D., Chan, K., Peters, S. T., Haynes, M. S., & Blankenship, D. D. (2026). Limited contribution of incoherent energy to detectable planetary radar sounding echoes. Planetary and Space Science 280, 106308. doi.org/10.1016/j.pss.2026.106308
  14. Wolfenbarger, N. S., Broome, A. L., Schroeder, D. M., Ermakov, A. I., Bolton, S. J., & Blankenship, D. D. (2026). Passive microwave radiometry and active radar sounding as complementary tools for geophysical investigations of icy ocean worlds. Journal of Geophysical Research: Planets, 131(3), e2025JE009301. doi.org/10.1029/2025JE009301
The library: 154 papers, by theme

Is there an ocean?

The ice shell: how thick, how warm

Ridges and the surface

Water inside the shell

Greenland’s firn and meltwater

Radar sounding

Methods, data and tools

Planets beyond the Solar System

How stars form

Ask me for a tour

The tools I use most

Code

  • Python
  • NumPy
  • SciPy
  • Matplotlib
  • Astropy

Lab

  • Vector network analyzer measurement and calibration
  • Dielectric measurement methods

Telescope data

  • IRAF/PyRAF spectral reduction

Building

  • Fabrication at Stanford's Lab64
Radio Glaciology LabLab GitHubMy research codeNASA Europa ClipperStanford Physics profileStanford Profiles

I'm happy to talk about any of this.

Write to me