About

Lujendra Ojha is an Associate Professor at Rutgers University in the Department of Earth and Planetary Sciences. His research interests focus on planetary science and geophysics. He is based at the Wright-Rieman Laboratories on the Busch Campus in Piscataway, NJ. His work involves studying planetary phenomena, contributing to the understanding of planetary environments and processes through geophysical methods.

Research topics

• Astrobiology
• Geology
• Geophysics
• Astrophysics
• Geochemistry
• Atmospheric sciences
• Physics
• Oceanography
• Paleontology
• Petrology
• Astronomy

Selected publications

• Europaquakes and Plumes Powered by Freezing-Driven Overpressure

  2026-03-14

  articleOpen access1st authorCorresponding

  We ask what may drive Europa’s putative intermittent plumes. We test whether shallow pockets of liquid water (i.e., sills) freezing within Europa's ice shell can power activity. We build a numerical model that couples heat flow, phase change, and pressure evolution, including the drop in melting temperature under pressure. As a sill freezes, the expansion of ice raises pressure; when a fracture opens, pressure falls and any supercooled liquid crystallizes quickly, producing bursts of solidification, pressure release, and re-pressurization. This cycle can yield sporadic venting and seismic events without a sustained conduit. Pressure-dependent melting shortens the total freezing time at depth and produces rarer but larger events, while elastic flexing of the ice roof reduces the event rate. For reasonable sill sizes and numbers, our model predicts late-stage spikes consistent with sporadic plumes and low-magnitude quakes. These results identify freezing sills as a self-contained engine for Europa’s activity and provide testable signatures for upcoming missions to seek Europaquakes and plumes.

  PublisherDOI

• Limited direct fluid exchange between the deep subsurface ocean and the shallow subsurface environment of Europa

  Research Square · 2025-09-18

  preprintOpen access1st authorCorresponding
  PublisherOA PDFDOI

• New observations of topographic slumps in Valles Marineris, Mars: Investigating the role of recurring slope lineae

  Icarus · 2025-02-10

  article
  PublisherDOI

• New Impacts on Mars: Unraveling Seismic Propagation Paths Through a Cerberus Fossae Impact Detection

  Geophysical Research Letters · 2025-02-03 · 9 citations

  articleOpen access

  Abstract To date, eight meteoroid impacts have been identified in the seismic record of NASA's InSight mission on Mars, occurring either within 300 km or beyond 3,500 km. We report the association of a high‐frequency marsquake, S0794a, with a new 21.5‐m‐diameter impact crater discovered at an intermediate distance of 1,640 km in the tectonically active Cerberus‐Fossae graben system. This impact enables the direct comparison between surface and subsurface sources, as well as providing the first data point in the critical gap between previous impacts, both in distance and crater size. Additionally, the location of this event necessitates a reassessment of assumed seismic raypaths that were thought to propagate along a slow crustal waveguide. We find that the raypaths instead penetrate and travel through the faster mantle, implying numerous identified marsquake epicenters should be relocated up to two times farther from InSight, with implications for seismically derived impact rates and regional seismicity.

  PublisherOA PDFDOI

• Gravity and Magnetic Field Signatures in Hydrothermally Affected Regions on Mars

  Journal of Geophysical Research Planets · 2025-04-01 · 4 citations

  articleOpen accessSenior author

  Abstract Multiple lines of evidence indicate that liquid water‐rock interactions occurred on ancient Mars, particularly within the crust, where hydrothermal systems have been hypothesized. Such hydrothermal circulation (HC) can significantly lower temperatures in the crust, thereby restricting the viscoelastic relaxation of impact craters. Craters with minimal relaxation are characterized by their large depth‐to‐diameter ratio and prominent Bouguer gravity anomalies. Additionally, HC can induce magnetic anomalies through chemical remanent magnetization (CRM). Consequently, if HC was widespread on Mars, the gravitational signatures of unrelaxed craters may correlate with their magnetic signatures. To investigate how HC influenced the magnetic characteristics of the Martian crust, we focus on the region surrounding several unrelaxed craters in the southern highlands, where hydrothermal activity was likely prevalent. We use a newly developed joint inversion approach and model magnetization and density in such regions to investigate how hydrothermal systems affect those parameters. The inversion approach makes use of a mutual information term in which models with a parameter relationship are favored, that is, models in which magnetization and density distributions are correlated. Despite showing large Bouguer gravity anomalies and forming over 3.75 billion years ago, when the Martian dynamo was most likely active, investigated craters and surrounding regions exhibit minimal magnetic anomalies. We propose that this lack of magnetic signatures is most likely due to demagnetization of the crust through CRM, induced by HC long after the Martian dynamo ceased. Our findings suggest that deep, long‐lived hydrothermal systems—likely fueled by heat‐producing elements—were present, potentially creating habitable conditions on early Mars.

  PublisherOA PDFDOI

• New Impacts on Mars: Unraveling Seismic Propagation Paths through a Cerberus Fossae Impact Detection

  2024-09-17

  article

  To date, eight meteoroid impacts have been identified in the seismic record of NASA's InSight mission on Mars, occurring either closer than 300~km or further than 3500~km. We report the association of a high-frequency marsquake, S0794a, with a new 21.5-m-diameter impact crater discovered at an intermediate distance of 1640~km in the tectonically active Cerberus-Fossae graben system. This impact enables the direct comparison between surface and subsurface sources, as well as providing the first data point in the critical gap between previous impacts, both in distance and crater size. Additionally, the location of this event necessitates a reassessment of previously assumed raypaths of seismic events thought to propagate along a slow crustal waveguide. We find that the raypaths instead penetrate and travel through the faster mantle, implying numerous identified marsquake epicentres should be relocated up to two times further from InSight, with implications for seismically derived impact rates and regional seismicity.

  PublisherDOI

• Martian crustal heat flow model

  Zenodo (CERN European Organization for Nuclear Research) · 2023-03-30

  articleOpen access

  The code of the Martian crustal heat flow model from Frizzell et al. (2023)

  PublisherDOI

• Insight into the formation mechanism of the Medusae fossae formation on Mars from magnetic field data

  Icarus · 2023-02-09 · 9 citations

  article1st authorCorresponding
  PublisherDOI

• Spatially variable crater morphology on the dwarf planet Haumea

  arXiv (Cornell University) · 2023-07-11

  preprintOpen accessSenior author

  Haumea, thought to be the Kuiper Belt's 3rd most massive object, has a fast 3.92 hr rotational period, resulting in its shape as a triaxial ellipsoid. Here, we make the first detailed predictions of Haumea's surface morphology, considering in particular effects stemming from its unique shape. Given observations have indicated Haumea's surface to be predominantly inert water ice, we predict crater characteristics, with craters likely to be the predominant surface feature on Haumea. In calculating Haumea's surface gravity, we find that g varies by almost two orders of magnitude, from a minimum of 0.0126 m/s^2 at the location of the equatorial major axis, to 1.076 m/s^2 at the pole. We also find a non-monotonic decrease in g with latitude. The simple to complex crater transition diameter varies from 36.2 km at Haumea's location of minimum surface gravity to 6.1 km at the poles. Equatorial craters are expected to skew to larger volumes, have depths greater by a factor of > 2, and have thicker ejecta when compared with craters at high latitudes. Considering implications for escape of crater ejecta, we calculate that Haumea's escape velocity varies by 62% from equator to pole. Despite higher escape velocities at the poles, impacts there are expected to have a higher mass fraction of ejecta escape from Haumea's gravitational well. Haumea may be unique among planet-sized objects in the solar system in possessing dramatic variations in crater morphology across its surface, stemming solely from changes in the magnitude of its surface gravity.

  PublisherOA PDFDOI

• Thermophysical assessment on the feasibility of basal melting in the south polar region of Mars

  arXiv (Cornell University) · 2023-02-22

  preprintOpen access1st authorCorresponding

  Bright basal reflectors in radargram from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) of the Martian south polar layered deposits (SPLD) have been interpreted to be evidence of subglacial lakes. However, this interpretation is difficult to reconcile with the low Martian geothermal heat flow and the frigid surface temperature at the south pole. We conduct a comprehensive thermophysical evolution modeling of the SPLD and show that subglacial lakes may only form under exceptional circumstances. Subglacial lakes may form if the SPLD contains more than 60 % dust volumetrically or extremely porous ice (>30 %), which is unlikely. A thick (>100 m) layer of dirty ice (>90% dust) at the base of the SPLD may also enable basal melting, resembling a sludge instead of a lake. Other scenarios enabling subglacial lakes in the SPLD are equally unlikely, such as recent magmatic intrusions at shallow depths.

  PublisherOA PDFDOI

Frequent coauthors

• J. J. Wray

  39 shared

• A. S. McEwen

  University of Arizona

  39 shared

• C. M. Dundas

  37 shared

• S. Karunatillake

  Louisiana State University

  30 shared

• S. Mattson

  26 shared

• Jacob Buffo

  Dartmouth College

  21 shared

• M. Chojnacki

  Planetary Science Institute

  17 shared

• Baptiste Journaux

  University of Washington

  17 shared

Labs

• Earth and Planetary Science Isotope Laboratory (EPSIL)PI

  The Earth and Planetary Science Isotope Laboratory (EPSIL) is a research group within the Department of Earth and Planetary Sciences at Rutgers University. The lab focuses on isotope geochemistry and its applications to understanding the Earth's past and present environments.

Education

• Ph.D., Geology

  University of Florida

  2009

• M.S., Geology

  University of Florida

  2005

• B.S., Geology

  University of Montana

  2003