NASA's Curiosity Research Articles

Radiation-Driven Destruction of Thiophene and Methyl-Substituted Thiophenes.

Thiophene and two derivatives (2-methylthiophene and 3-methylthiophene) have been detected on the surface of Mars with the Sample Analysis at Mars instrument suite onboard NASA's Curiosity rover. Thiophene could serve as a secondary chemical biosignature since the secondary biosynthesis of thiophene is considered an important production pathway. However, it is critical to understand the abiotic formation and destruction of thiophene and its derivatives since these pathways could affect the molecules' stabilities on planetary surfaces over geological timescales. Here, we present the radiolytic destruction kinetics of thiophene, 2-methylthiophene, and 3-methylthiophene as single-component ices and when diluted in water ice at low temperatures. Using infrared spectroscopy, we determined the destruction rate constants and extrapolated our radiolytic half-lives to the surface of Mars, assuming the measured and modeled surface dose rates. We found that our rate constants strongly depend on temperature and presence of water ice. Based on our determined radiolytic half-life for thiophene under conditions most similar to those of thiophene groups in Martian macromolecules, we expect thiophene to be stable on the surface for significantly longer than the Martian surface exposure age of sites in Gale crater where thiophenes have been detected.

Water and Chlorine in the Martian Subsurface Along the 27 km Traverse of NASA's Curiosity Rover According to DAN Measurements: 2. Results for Distinct Geological Regions

AbstractThis paper is Part II of a double‐paper series that presents the abundance of water and chlorine along with other neutron‐absorbing elements in the shallow subsurface of Gale crater based on measurements by the Dynamic Albedo of Neutron (DAN) instrument onboard NASA's Curiosity rover. Initial results were represented as pixels on map data products from both DAN active and passive measurements made along the 27‐km traverse of the rover, corresponding to the mission period from landing on the martian surface in August 2012 through December 2021. In Part II, the contents of water and chlorine along with other neutron absorbers are studied separately for distinct geological regions along the traverse. Mean values and sample variances of these values are presented for each region. Water‐equivalent hydrogen (WEH) measurements show variability within the Jura member of the Murray formation and increase within the Carolyn Shoemaker formation. A large fraction of stratigraphic units (e.g., Bradbury, Sheepbed, Pahrump Hills and others) have mean WEH values between 2 and 3 wt.%, while units in the second part of the traverse (Jura, Knockfarrill Hill, Glasgow, Pontours) have mean values of WEH above 3 wt.%. The mean absorption‐equivalent chlorine value has no large variations for all tested geologic units; it is equal to around 1% for all of them.

Neutron emission on the surface of Mars

The neutron emission of Mars is known to be produced due to the bombardment of Martian surface by Galactic Cosmic Rays (GCRs). As evidenced by numerical simulation, the intensity of neutron emission on the planetary surface is much larger than that of the neutron emission at the orbital altitude due to multiple reflections of the neutrons emitted from soil by the atmosphere. The code developed for simulations was validated using the experimental data of neutron emission acquired in the Gale crater by the RAD and DAN instruments aboard the NASA's Curiosity rover. Neutron emission was simulated for two Martian areas: the dry Solis Planum territory and the bottom of the Valles Marineris system of canyons, which is thought to be the most wet equatorial spot on Mars. For both areas a strong effect is found, showing a considerable difference between the neutron emission on the surface and at the altitude of a typical orbit. It was also shown that surface emission in these two areas is quite different due to the difference of mass fraction of water in the shallow subsurface. Finally, the seasonal variations of neutron emission in these areas due to the atmospheric seasonal changes are also estimated.

Detectability of carbon with ChemCam LIBS: Distinguishing sample from Mars atmospheric carbon, and application to Gale crater

Onboard NASA's Curiosity rover, the ChemCam LIBS instrument has provided a wealth of information on the chemistry of rocks within Gale crater. Here, we use ChemCam in order to search for carbonates among the >3500 individual targets analyzed by this instrument. Because the carbon-lines are a combination of signal from the CO2-rich atmosphere and possible carbon from the targets, we developed a laboratory-based univariate calibration obtained under Mars-like atmosphere. We measured different type of carbon-bearing samples (sediments, coals, carbonates) and their mixture with a basaltic powder. Based on this work, the preferred approach to qualitatively assess carbon under a CO2-rich atmosphere is to use a ratio to an oxygen line (777 nm) and the estimated limit of detection for carbon in a single LIBS point are found to be of 4.5 wt% and 6.9 wt% for reduced and organic carbon, respectively. Considering carbonate, this LOD correspond to about 50 wt% carbonate in the analyzed volume.Analysis of data obtained on Mars by ChemCam up to sol 3350 reveals the presence of a correlation between the intensity of carbon and oxygen lines, as observed in the laboratory, confirming that most carbon signal is related to ionization of the atmosphere. Some variability in the carbon signal appears related to the physical state of the atmosphere (density, temperature).Based on a combined analysis of carbon lines and major element compositions (Ca, Fe, Mg), there was no detection of carbonate in the ChemCam dataset up to sol 3355. Therefore, we conclude that carbonate was not present as a major constituent (>50%) in the ChemCam LIBS targets, and that soils are not enriched in carbon beyond the limit of detection. The dominant salts present are sulfate, chlorides, and the lack of carbonates in Gale, while observed in Jezero, may at least partly be related to a difference in protolith.

Depth Distribution of Chlorine at Gale Crater, Mars, as Derived From the DAN and APXS Experiments Onboard the Curiosity Rover

AbstractThe subsurface chlorine depth distribution at Gale crater has been studied using measurements from the Alpha Particle X‐ray Spectrometer (APXS) and Dynamic Albedo of Neutrons (DAN) instruments onboard NASA's Curiosity Mars rover. These measurements have been acquired at or near ∼30 drill holes made by Curiosity along its 30 km drive. APXS measured a ∼15 micron surface layer of bedrock and shallow depth of ∼5 cm of drill tailings. DAN is sensitive to the bulk (∼50 cm depth) chlorine abundance and that of other neutron absorbing elements. Joint analysis of APXS and DAN data shows that the chlorine distribution at Gale crater consists of two components: surficial chlorine with concentrations >1 wt.%, possibly controlled by aeolian deposition of Cl‐rich dust and surface alteration, and subsurface chlorine with concentrations <1 wt.%, likely a result of groundwater activity in the past.

Sedimentary Organics in Glen Torridon, Gale Crater, Mars: Results From the SAM Instrument Suite and Supporting Laboratory Analyses

AbstractThe Sample Analysis at Mars (SAM) suite instrument on board NASA's Curiosity rover has characterized the inorganic and organic chemical composition of seven samples from the Glen Torridon (GT) clay‐bearing unit. A variety of organic molecules were detected with SAM using pyrolysis (up to ∼850°C) and wet chemistry experiments coupled with evolved gas analysis (EGA) and gas chromatography‐mass spectrometry. SAM EGA and GCMS analyses revealed a greater diversity and abundance of sulfur‐bearing aliphatic and aromatic organic compounds in the sediments of this Gale crater unit than earlier in the mission. We also report the detection of nitrogen‐containing, oxygen‐containing, and chlorine‐containing molecules, as well as polycyclic aromatic hydrocarbons found in GT, although the sources of some of these organics may be related to the presence of chemical reagents in the SAM instrument background. However, sulfur‐bearing organics released at high temperature (≥600°C) are likely derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources and consistent with the presence of recalcitrant organic materials in the sample. The SAM measurements of the GT clay‐bearing unit expand the inventory of organic matter present in Gale crater and is also consistent with the hypothesis that clay minerals played an important role in the preservation of ancient refractory organic matter on Mars. These findings deepen our understanding of the past habitability and biological potential of Gale crater.

Water and Chlorine in the Martian Subsurface Along the Traverse of NASA's Curiosity Rover: 1. DAN Measurement Profiles Along the Traverse.

This paper presents estimates of the water and chlorine contents in the subsurface of Gale crater based on the measurements by the Dynamic Albedo of Neutrons (DAN) instrument onboard the NASA Curiosity rover. It is Part 1 of a two-paper series. Data derived both from DAN active and passive measurements are presented in discrete surface areas (pixels) assuming a homogeneous distribution of water within the DAN sensing depth (60cm) along the traverse of the rover. It is shown that the content of hydrogen, reported as Water Equivalent Hydrogen, varies between almost zero and a maximum of (6.1±0.7) wt.%. The content of absorption equivalent chlorine varies between almost zero and (2.6±0.2) wt.%. Such variations are thought to be related to the different geological processes and environmental conditions present in the strata along the traverse during the evolutionary history of Gale crater. The second paper (Part 2) studies particular properties of water and abundances of neutron absorbing elements at distinct geological regions, that the rover crossed on its way.

The Martian surface radiation environment at solar minimum measured with MSL/RAD

The radiation environment at the surface of Mars is mainly dominated by incoming galactic cosmic rays (GCRs) that propagate through the atmosphere, with sporadic strong contributions from solar energetic particles (SEPs). The main driver for changes in the radiation field, on time scales of years, is the solar modulation of the GCR flux. During times of higher solar activity, GCRs are more strongly attenuated, resulting in highest GCR fluxes during solar minimum and lowest fluxes at solar maximum. We report dosimetric measurements conducted with the Radiation Assessment Detector (RAD) from November 2019 to October 2020 during the recent deep solar minimum. RAD has been operating on board NASA's Curiosity rover on Mars since August 2012. We bring these measurements into context with RAD measurements from 2012 to 2013 around the (weak) maximum of Solar Cycle 24. The results show the impact of the changing solar modulation from 2012 to 2020 on the Martian surface radiation environment and have implications for future human exploration missions of Mars. We find that while the overall radiation dose rate has increased significantly by 50% between the two time frames, the biologically highly relevant dose equivalent rate shows a modest increase of 13%, yielding interesting input for the timing of such Mars missions within the solar cycle. We also report the first results of the analysis of the flux of medium-energy protons with 100–300 MeV on the Martian surface, yielding an important additional, in-situ measured data point for validating radiation transport models.

Spatiotemporal characterization of the laser-induced plasma plume in simulated Martian conditions

With ChemCam on NASA's Curiosity rover, SuperCam on NASA's Perseverance rover, and MarSCoDe on the Zhurong rover of the China National Space Administration, there are currently three instruments on Mars that employ laser-induced breakdown spectroscopy (LIBS) to analyze the chemical composition of Martian rocks and soils. With more than 880,000 LIBS measurements on Mars by ChemCam alone, the LIBS technique has been proven to be uniquely qualified for the in-situ robotic exploration of planetary surfaces. Since the laser-induced plasma exhibits a complex spatiotemporal evolution that has a significant impact on the recorded LIBS spectra, fundamental investigations of the plasma propagation and the spatial distributions of the plasma emissions can provide important insight that can help to improve the analysis of Martian LIBS spectra. Here we present first results from our LIBS plasma imaging setup, which allows us to spatially and temporally resolve the spectral emissions from the laser-induced plasma in simulated Martian atmospheric conditions. Investigating a calcium sulfate sample, we find that the commonly applied assumption of a nearly isothermal and homogeneous plasma with a colder outer layer is not sufficient to describe the laser-induced plasma on Mars. Instead, different spectral features show unique spatial distributions that suggest a strong influence of the outgoing shock wave. After plasma formation, the plasma center is found to rapidly become colder and more rarefied than the outer plasma regions. Molecular emissions are found to originate in this cold plasma center.

Influence of Calcium Perchlorate on the Search for Martian Organic Compounds with MTBSTFA/DMF Derivatization.

N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA), mixed with the solvent N,N-dimethylformamide (DMF), is used as a derivatizing reagent by the Sample Analysis at Mars (SAM) experiment onboard NASA's Curiosity rover and will soon be utilized by the Mars Organic Molecule Analyzer experiment onboard the ESA/Roscosmos Rosalind Franklin rover. The pyrolysis products of MTBSTFA, DMF, and the MTBSTFA/DMF mixtures, obtained at different temperatures, were analyzed. Two different pyrolysis modes were studied, flash pyrolysis and ramp pyrolysis (35°C/min), to evaluate the potential influence of the sample heating speed on the production of products in space chromatographs. The effect of the presence of calcium perchlorate on the pyrolysis products of MTBSTFA/DMF was also studied to ascertain the potential effect of perchlorate species known to be present at the martian surface. The results show that MTBSTFA/DMF derivatization should be applied below 300°C when using flash pyrolysis, as numerous products of MTBSTFA/DMF were formed at high pyrolysis temperatures. However, when an SAM-like ramp pyrolysis was applied, the final pyrolysis temperature did not appear to influence the degradation products of MTBSTFA/DMF. All products of MTBSTFA/DMF pyrolysis are listed in this article, providing a major database of products for the analysis of martian analog samples, meteorites, and the in situ analysis of martian rocks and soils. In addition, the presence of calcium perchlorate does not show any obvious effects on the pyrolysis of MTBSTFA/DMF: Only chloromethane and TBDMS-Cl (chloro-tertbutyldimethylsilane) were detected, whereas chlorobenzene and other chlorine-bearing compounds were not detected. However, other chlorine-bearing compounds were detected after pyrolysis of the Murchison meteorite in the presence of calcium perchlorate. This result reinforces previous suggestions that chloride-bearing compounds could be reaction products of martian samples and perchlorate.

Updated Perspectives and Hypotheses on the Mineralogy of Lower Mt. Sharp, Mars, as Seen From Orbit

AbstractPrevious studies have shown that Mt. Sharp has stratigraphic variation in mineralogy that may record a global transition from a climate more conducive to clay mineral formation to one marked by increased sulfate production. To better understand how small‐scale observations along the traverse path of NASA's Curiosity rover might be linked to such large‐scale processes, it is necessary to understand the extent to which mineral signatures observed from orbit vary laterally and vertically. This study uses newly processed visible‐shortwave infrared Compact Reconnaissance Imaging Spectrometer for Mars data and corresponding visible images to reexamine the mineralogy of lower Mt. Sharp, map mineral distribution, and evaluate stratigraphic relationships. We demonstrate the presence of darker‐toned strata that appears to be throughgoing with spectral signatures of monohydrated sulfate. Strata above and below this zone are lighter‐toned and contain polyhydrated sulfate and variable distribution of Fe/Mg clay minerals. Clay minerals are observed at multiple stratigraphic positions; unlike the kieserite zone these units cannot be traced laterally across Mt. Sharp. The kieserite zone appears to be stratigraphically confined, but in most locations the orbital data do not provide sufficient detail to determine whether mineral signatures conform to or cut across stratigraphic boundaries, leaving open the question as to whether the clay minerals and sulfates occur as detrital, primary chemical precipitates, and/or diagenetic phases. Future observations along Curiosity's traverse will help distinguish between these possibilities. Rover observations of clay‐bearing strata in northwest Mt. Sharp may be more reflective of local conditions that could be distinct from those associated with other clay‐bearing strata.

Evidence for hydraulic fracturing at Gale crater, Mars: Implications for burial depth of the Yellowknife Bay formation

NASA's Curiosity rover identified a formerly habitable environment within strata informally known as the Yellowknife Bay formation. The stratigraphic relationship, and thus depositional age, of these rocks relative to other geologic units in Gale crater is not clear from orbital data alone. If part of lower Aeolis Mons (informally known as Mount Sharp), the Yellowknife Bay rocks have been deeply buried and exhumed prior to 3.2–3.3 Ga. If part of younger alluvial fan deposits, however, they likely have never experienced more than ∼100 m of burial. Knowledge of burial history can thus constrain the stratigraphic placement of Yellowknife Bay and the habitable environment preserved therein. The mechanics of natural hydraulic fractures observed in mudstone at YKB allow us to evaluate its burial history and imply a minimum burial depth of 1.2 km. This is consistent with burial by the entirety of lower Mount Sharp and a depositional age of ∼3.6–3.8 Ga, providing observation-based evidence that Mount Sharp was once much more laterally extensive than its present form. Rocks of the Yellowknife Bay formation thus represent the oldest strata that Curiosity will encounter during its journey in Gale crater, and any additional habitable environments discovered along Curiosity's future path represent conditions at younger times.

In situ evidence for continental crust on early Mars

Understanding of the geologic evolution of Mars has been greatly improved by recent orbital(1-3), in situ(4,5) and meteorite(6-8) data, but insights into the earliest period of Martian magmatism (4.1 to 3.7 billion years ago) remain scarce(9). The landing site of NASA's Curiosity rover, Gale crater, which formed 3.61 billion years ago(10) within older terrain(11), provides a window into this earliest igneous history. Along its traverse, Curiosity has discovered light-toned rocks that contrast with basaltic samples found in younger regions(12). Here we present geochemical data and images of 22 specimens analysed by Curiosity that demonstrate that these light-toned materials are feldspar-rich magmatic rocks. The rocks belong to two distinct geochemical types: alkaline compositions containing up to 67 wt% SiO2 and 14 wt% total alkalis (Na2O + K2O) with fine-grained to porphyritic textures on the one hand, and coarser-grained textures consistent with quartz diorite and granodiorite on the other hand. Our analysis reveals unexpected magmatic diversity and the widespread presence of silica- and feldspar-rich materials in the vicinity of the landing site at Gale crater. Combined with the identification of feldspar-rich rocks elsewhere(9,13,14) and the low average density of the crust in the Martian southern hemisphere(15), we conclude that silica-rich magmatic rocks may constitute a significant fraction of ancient Martian crust and may be analogous to the earliest continental crust on Earth.

Curiosity Rover Rock Analysis Indicates Past Habitability on Mars

Following an analysis of a Martian rock sample that was drilled into by an instrument on board NASA's Curiosity Rover, agency and project scientists announced at a 12 March briefing that they now have evidence indicating that an area near where the rover landed in Gale Crater last August could have once supported ancient microbial life.

Landing a Spacecraft on Mars

How much software does it take to land a spacecraft safely on Mars, and how do you make all that code reliable? This column describes such a software development process. The first Web extra at http://mars.jpl.nasa.gov/multimedia/videos/movies/miam20121218/miam20121218-1280.mov is a 60-second video from NASA's Jet Propulsion Laboratory that shows how NASA's Mars rover drivers operate the vehicles from millions of miles away. The second Web extra at http://mars.jpl.nasa.gov/multimedia/videos/movies/msl20120827_curiositycommunicates/msl20120827_curiositycommunicates-1280.mov is an animated video showing how NASA's Curiosity rover communicates with Earth via two of NASA's Mars orbiters, Mars Reconnaissance Orbiter (MRO) and Odyssey, and the European Space Agency's Mars Express. The third Web extra at http://mars.jpl.nasa.gov/multimedia/videos/movies/CoM20121207/CoM20121207-1280.mov is a video discussing the scientific study by NASA's Curiosity Mars rover at Rocknest.

Random Sample

NASA's Curiosity rover has extracted the first sample of the interior of Mars, psychologists will soon have a major prize of their own, and horsemeat went out of style thanks to Christianity .

Curiosity rover LEGO® version could land soon

Now that NASA's Curiosity rover has landed on Mars, a smaller LEGO® plastic brick construction version could be landing in toy stores. Less than 2 weeks after Curiosity set down on 5 August, a LEGO® set concept model designed by a mechanical and aerospace engineer who worked on the real rover garnered its 10,000th supporter on the Web site of CUUSOO, a Japanese partner of the LEGO® group. That milestone triggered a company review that began in September 2012 to test the model's “playability, safety, and ft with the LEGO® brand,” according to a congratulatory statement from the company to designer Stephen Pakbaz. Pakbaz told Eos that he has been an avid LEGO® and space exploration fan for most of his life. “For me, creating a LEGO® model of Curiosity using my firsthand knowledge of the rover was inevitable. What I enjoyed most was being able to faithfully replicate and subsequently demonstrate the rocker‐bogie suspension system to friends, family, and coworkers,” he noted, referring to the suspension system that allows the rover to climb over obstacles while keeping its wheels on the ground. Pakbaz, who is currently with Orbital Sciences Corporation, was involved with aspects of the rover while working at the Jet Propulsion Laboratory from 2007 to 2011 as a mechanical engineer.

President's message: Dues increase will help build the foundation for AGU's future success

The world is a very different place than it was 43 years ago. In 1969, Jimi Hendrix rocked the legendary Woodstock music festival, Neil Armstrong took the first steps on the Moon, and U.S. drivers paid an average of 35 cents a gallon for gas. Today, digital music files have replaced vinyl records, NASA's Curiosity rover is transmitting data and imagery from the surface of Mars, and a growing number of cars run on alternative fuels. In the same way, 43 years ago AGU was a very different organization. Membership hovered around 10,000, and the Fall Meeting was still in its infancy. Today, AGU's membership has increased to more than 61,000, Fall Meeting attendance has topped 20,000, and an entire generation of geoscientists who weren't even born in 1969 now comprises 28% of our current membership.

Around the World

In science news around the world this week, NASA's Curiosity rover will contaminate Mars samples with Teflon from the rover's machinery, the World Health Organization warned that gonorrhea could soon become untreatable, a coal mine planned in Queensland was halted citing concerns that it would damage Australia's Great Barrier Reef, the Nuffield Council on Bioethics ruled that mitochondrial disease therapy is ethical, California has rejected a proposed new tobacco tax, French research unions are protesting the government's new funding plan, and NASA has axed a mission to study black holes and neutron stars.