About

Scott M. McLennan is a Distinguished Toll Professor in the Department of Geosciences at Stony Brook University. His research focuses on evaluating the evolution of planetary crusts and surficial processes primarily through the chemical composition of sedimentary rocks. He has contributed significantly to understanding planetary history by analyzing sedimentary compositions, which record tectonic, climatic, and geographic conditions during deposition, thus enabling the tracing of surface evolution on Earth and Mars. Professor McLennan has extensive involvement with planetary missions to Mars, including the Viking, Pathfinder, Spirit, Opportunity, Phoenix, Curiosity, and Perseverance missions. His role on these missions has involved supporting mission planning, operations, and conducting research with the data returned. His work has provided important constraints on the geological history of Mars, especially through the chemical and mineralogical analysis of surface materials. He has collaborated with various orbital and in situ instruments, and his research has refined models of Martian crust and mantle composition, integrating geophysical data from missions like InSight and orbital spectroscopy. He is also known for his contributions to the understanding of planetary crusts, as summarized in his co-authored book 'Planetary Crusts: Their Composition, Origin, and Evolution,' which received the 2010 Award for Best Reference Work from the Geoscience Information Society. Throughout his career, Professor McLennan has supervised numerous students and postdoctoral researchers, and his work continues to advance the understanding of planetary surface processes and crustal evolution.

Research topics

• Geology
• Astrobiology
• Geophysics
• Physics
• Computer Science
• Remote sensing
• Petrology
• Materials science
• Geochemistry
• Astronomy
• Optics
• Seismology
• Telecommunications

Selected publications

• 123 Failure to follow-up: a series of unfortunate events

  The American Journal of the Medical Sciences · 2025-01-15

  article1st authorCorresponding
  PublisherDOI

• What is Mars (not) made of? A joint isotopic, geochemical and geophysical analysis

  Icarus · 2025-06-14 · 5 citations

  articleOpen access

  The terrestrial planets are believed to have accreted from chondritic meteorites of widely varying composition. Yet, making planets from known meteoritic material has proved elusive, be it their nucleosynthetic isotopic anomalies, bulk chemistry or geophysical properties. Because of the inherent non-uniqueness of meteoritic mixing models based on isotopes alone, combining geochemical and geophysical observations is key to identifying the nature of the building blocks of the terrestrial planets. Here, we integrate the recent proliferation of data in the form of geophysical measurements pertaining to Mars’s interior structure from the recent InSight mission including its astronomic-geodetic response, the chemical and isotopic compositions of undifferentiated and differentiated meteorites, and observational constraints on trace element abundances (K/Th ratio) in order to make new inferences on the constitution and provenance of Mars. Using stochastic mixing models of meteoritic material, we find that ∼ 0.02% of mixtures, consisting primarily of ordinary- and enstatite chondrites and, to a lesser extent, achondritic material, are able to reproduce the isotopic signature of Mars. Of these, however, none match the geophysical or Mg/Si and K/Th constraints, indicating that Mars is unlikely to have formed from known unmodified meteoritic material. Instead, relatively oxidised building blocks that are intrinsic to the inner solar system and underwent evaporation/condensation processes that lead to volatile-element depletion patterns unlike those in any known meteorite group, would be consistent with the isotopic, geochemical and geophysical properties of Mars. • Provenance models for Mars are unable to fit geochemical and -physical properties. • Isotopically valid models fail to match key elemental ratios and Mars’ geophysics. • Mars must have formed from extant or unsampled meteoritic material.

  PublisherDOI

• Scientific Laws and Myths, Ockham’s Razor, and Multiple Working Hypotheses

  Elements · 2024-06-01

  articleOpen access1st authorCorresponding
  PublisherOA PDFDOI

• Stuart Ross Taylor 1925–2021

  Historical Records of Australian Science · 2024-07-04

  article1st authorCorresponding

  Stuart Ross Taylor, born and raised in New Zealand, spent most of his career at the Australian National University where his laboratory research focused on trace element geochemistry. He made fundamental contributions toward understanding the composition and evolution of the Moon and Earth, the origin of tektites and solar system evolution. He carried out the first-ever chemical analyses of Apollo 11 lunar samples. Ross Taylor received many awards and honours and was a Companion of the Order of Australia.

  PublisherDOI

• <i>Agrobacterium</i>-mediated transformation of rose meristem in vitro

  Acta Horticulturae · 2024-09-01 · 1 citations

  article
  PublisherDOI

• Samples Collected From the Floor of Jezero Crater With the Mars 2020 Perseverance Rover

  Journal of Geophysical Research Planets · 2023-02-09 · 100 citations

  articleOpen access

  Abstract The first samples collected by the Mars 2020 mission represent units exposed on the Jezero Crater floor, from the potentially oldest Séítah formation outcrops to the potentially youngest rocks of the heavily cratered Máaz formation. Surface investigations reveal landscape‐to‐microscopic textural, mineralogical, and geochemical evidence for igneous lithologies, some possibly emplaced as lava flows. The samples contain major rock‐forming minerals such as pyroxene, olivine, and feldspar, accessory minerals including oxides and phosphates, and evidence for various degrees of aqueous activity in the form of water‐soluble salt, carbonate, sulfate, iron oxide, and iron silicate minerals. Following sample return, the compositions and ages of these variably altered igneous rocks are expected to reveal the geophysical and geochemical nature of the planet's interior at the time of emplacement, characterize martian magmatism, and place timing constraints on geologic processes, both in Jezero Crater and more widely on Mars. Petrographic observations and geochemical analyses, coupled with geochronology of secondary minerals, can also reveal the timing of aqueous activity as well as constrain the chemical and physical conditions of the environments in which these minerals precipitated, and the nature and composition of organic compounds preserved in association with these phases. Returned samples from these units will help constrain the crater chronology of Mars and the global evolution of the planet's interior, for understanding the processes that formed Jezero Crater floor units, and for constraining the style and duration of aqueous activity in Jezero Crater, past habitability, and cycling of organic elements in Jezero Crater.

  PublisherOA PDFDOI

• Global crustal thickness revealed by surface waves orbiting Mars

  2023-03-06 · 1 citations

  preprintOpen access

  We report observations of Rayleigh waves that orbit around Mars up to three times following the S1222a marsquake. Averaging these signals, we find the largest amplitude signals at 30 s and 85 s central period, propagating with distinctly different group velocities of 2.9 km/s and 3.8 km/s, respectively. The group velocities constraining the average crustal thickness beneath the great circle path rule out the majority of previous crustal models of Mars that have a &gt;200 kg/m3 density contrast across the dichotomy. We find that the thickness of the martian crust is 42-56 km on average, and thus thicker than the crusts of the Earth and Moon. Together with thermal evolution models, a thick martian crust suggests that the crust must contain 50-70% of the total heat production to explain present-day local melt zones in the interior of Mars.

  PublisherOA PDFDOI

• High‐Frequency Receiver Functions With Event S1222a Reveal a Discontinuity in the Martian Shallow Crust

  Geophysical Research Letters · 2023-03-07 · 21 citations

  articleOpen access

  Abstract The shallow crustal structure of Mars records the evolutionary history of the planet, which is crucial for understanding the early Martian geological environment. Until now, seismic constraints on the Martian crust have come primarily from the receiver functions (RFs). However, analysis of the Mars RFs did not focus on the shallow structure (1–5 km) so far due to the limitation of the signal‐to‐noise ratio at high frequencies for most events. Here, we take advantage of the S1222a and six other marsquakes, which exhibit high signal‐to‐noise ratios, to probe the shallow structure of Mars. We observe a converted S‐wave at approximately 1 s after the direct P‐wave in the high‐frequency P‐wave RFs. This suggests a discontinutity at 2‐km depth between highly fractured and more coherent crustal materials.

  PublisherOA PDFDOI

• Constraints on Martian Crustal Lithology from Seismic Velocities by InSight

  2023-02-26

  preprintOpen access

  Analysis of data from the seismometer SEIS on NASA&amp;#8217;s InSight mission has by now provided a wealth of information on the crustal structure of Mars, both beneath the lander and at other locations on the planet. Here, we collect the P- and S-wave velocity information for kilometer-scale crustal layers available up to now and compare it to predictions by rock physics models to guide the interpretation in terms of crustal lithology.Modeling is performed based on the Hertz-Mindlin model for un- or poorly consolidated sediments, Dvorkin and Nur&amp;#8217;s cemented-sand model for consolidated sediments and Berryman&amp;#8217;s self-consistent approximation to simulate cracked rocks. Considered lithologies include basalt, andesite, dacite, kaolinite, and plagioclase, and cementation due to calcite, gypsum, halite and ice. We use Gassmann fluid substitution to study the effect of liquid water instead of atmosphere filling the pores or cracks.Below the lander, available constraints are based on Ps-receiver functions and vertical component autocorrelations for SV- and P-wave velocities, whereas SH-reflections and SsPp phases provide additional information on SH- and P-wave velocities in the uppermost 8-10 km, respectively. SS and PP precursors at the bouncing point of the most distant marsquake contain information on crustal velocities at a near-equatorial location far from InSight. Surface wave observations from two large impacts as well as the largest marsquake recorded by InSight provide average crustal velocities along their raypaths, which are distinct from the body wave results.The subsurface structure beneath the lander can be explained by 2 km of either unconsolidated basaltic sands, clay with a low amount (2%) of cementation, or cracked rocks (e.g. basalts with at least 12% porosity). Within the range of lithologies considered, the seismic velocities can neither be explained by intact rocks, nor rocks with completely filled pores, e.g. by ice, nor by fluid-saturated rocks. Below, down to a depth of about 10 km beneath InSight, both P- and SV-wave velocities are consistent with fractured basaltic rocks or plagioclase of at least 5% porosity, depending on crack aspect ratios. About 10% of that porosity needs to have a preferred orientation to explain the observed anisotropy. For porosities exceeding 12%, the measured velocities would also be consistent with water-saturated rocks. The transition to higher velocities at about 10 km depth beneath InSight can be modeled by more intact material, i.e. a porosity reduction by 50% compared to the layer above, which can be achieved by either cementation or a lower initial porosity.The SV-velocities derived by surface waves down to 25-30 km depth, averaging over a large part of Mars, are consistent with basalts of a porosity of less than 5% or nearly intact plagioclase. They could also be explained by rocks with a higher porosity if pores are filled by ice, but that is unlikely for the whole depth range considered. The velocities at larger depth, i.e. below about 20 km beneath InSight and 25-30 km along the surface wave paths, are consistent with intact basalt.

  PublisherDOI

• Petrological Traverse of the Olivine Cumulate Séítah Formation at Jezero Crater, Mars: A Perspective From SuperCam Onboard Perseverance

  Journal of Geophysical Research Planets · 2023-05-30 · 60 citations

  articleOpen access

  Abstract Séítah is the stratigraphically lowest formation visited by Perseverance in the Jezero crater floor. We present the data obtained by SuperCam: texture by imagery, chemistry by Laser‐Induced Breakdown Spectroscopy, and mineralogy by Supercam Visible and Infrared reflectance and Raman spectroscopy. The Séítah formation consists of igneous, weakly altered rocks dominated by millimeter‐sized grains of olivine with the presence of low‐Ca and high‐Ca pyroxenes, and other primary minerals (e.g., plagioclase, Cr‐Fe‐Ti oxides, phosphates). Along a ∼140 m long section in Séítah, SuperCam analyses showed evidence of geochemical and mineralogical variations, from the contact with the overlying Máaz formation, going deeper in the formation. Bulk rock and olivine Mg#, grain size, olivine content increase gradually further from the contact. Along the section, olivine Mg# is not in equilibrium with the bulk rock Mg#, indicating local olivine accumulation. These observations are consistent with Séítah being the deep ultramafic member of a cumulate series derived from the fractional crystallization and slow cooling of the parent magma at depth. Possible magmatic processes and exhumation mechanisms of Séítah are discussed. Séítah rocks show some affinity with some rocks at Gusev crater, and with some Martian meteorites suggesting that such rocks are not rare on the surface of Mars. Séítah is part of the Nili Fossae regional olivine‐carbonate unit observed from orbit. Future exploration of Perseverance on the rim and outside of the crater will help determine if the observations from the crater floor can be extrapolated to the whole unit or if this unit is composed of distinct sub‐units with various origins.

  PublisherOA PDFDOI

Frequent coauthors

• J. R. Johnson

  Johns Hopkins University Applied Physics Laboratory

  430 shared

• K. E. Herkenhoff

  Astrogeology Science Center

  427 shared

• R. E. Arvidson

  328 shared

• J. F. Bell

  Arizona State University

  322 shared

• H. Y. McSween

  University of Tennessee at Knoxville

  322 shared

• R. V. Morris

  Johnson Space Center

  292 shared

• J. P. Grotzinger

  California Institute of Technology

  288 shared

• W. H. Farrand

  Space Science Institute

  282 shared

Labs

• Scott McLennan LabPI

Education

• B.S.

  University of Western Ontario

  1975

• M.S.

  University of Western Ontario

  1977

• Ph.D.

  Australian National University

  1981

Awards & honors

• Planetary Crusts: Their Composition, Origin, and Evolution (…