Meteoritic Material Research Articles

Structural transformations and magnetic properties of plastically deformed FeNi-based alloys synthesized from meteoritic matter

In this work we investigated FeNi-based alloys synthesized from the cosmic matter of Morasko Meteorite (MM). The fall of Morasko iron meteorite is one of the biggest known in Central Europe and it has been dated to take place about five thousand years ago. It is known that iron meteorites contain hard magnetic tetrataenite phase (L10 FeNi), which has not been synthesized on the Earth in significant amount in the bulk form yet, because of very sluggish diffusion of Fe and Ni atoms below the disorder-order temperature of 320 °C. Firstly we doped the metallic part of Morasko Meteorite with Ni to obtain nearly equiatomic composition Fe51Ni49, which is the composition of pure tetrataenite.Further synthesis steps (melt-spinning, high pressure torsion, isothermal annealing at Ta = 320 °C for τa = 720 h) were undertaken to induce structural disorder and to observe changes in the structure/microstructure of the meteorite melt with nickel and its magnetic behavior. The presence of fcc FeNi with slightly varying lattice constant was confirmed at each step of the treatment. It evolved from the initial value of a = 3.589 ± 0.001 Å in the as-quenched state, through 3.591 ± 0.001 Å after 10 revolutions in the high pressure torsion process, to the maximum value of 3.593 ± 0.001 Å after 30 revolutions of anvils. No significant impact of further application of stress (50 revolutions) was noted, as the lattice parameter changed within the uncertainty limit. After annealing, the lattice parameter decreased to the initial value of the as-quenched sample (a = 3.589 ± 0.001 Å). The observed broadening of the peaks in the X-ray diffraction patterns may be attributed to the presence of microstrains and refinement of crystallites. Both contributions were determined using the Williamson-Hall method. In the initial state, the domain sizes were of about 100 ± 17 nm and diminished to 36 ± 11 nm after application of stress. Further isothermal annealing did not change the crystallites size, which was evaluated to be 35 ± 9 nm. Microstrains in the initial state were determined as (0.039 ± 0.017)10−3 and increased significantly to (0.562 ± 0.060)10−3 after 30 revolutions of anvils. Isothermal annealing decreased microstrains to (0.215 ± 0.071)10−3. After application of stress, the coercivity and remanence were enhanced, while subsequent isothermal annealing caused their decrease. Moreover, severe plastic deformation facilitated saturation of magnetization. As-quenched sample reached saturation at a magnetic field of about 2 T, while for high pressure torsion processed alloy this value was significantly reduced.

Structural elucidation of soluble organic matter: Application to Titan's haze

The origin and evolution of organic matter in the solar system intertwines astrobiology and planetary geochemistry issues. To observe the contribution of atmospheric processes in the formation of complex organic matter, one of the most intensively studied objects in the outer solar system is Titan, the largest moon of Saturn. Its reducing atmosphere of methane and nitrogen hosts a thick, permanent, nitrogen-rich, organic haze, whose complex composition remains largely unknown. Due to the measurement of species at large mass-to-charge ratio and infrared information from the Cassini-Huygens mission, polyaromatic hydrocarbons (PAHs) based structure for this haze has been suggested. Here, we propose a snapshot of the global chemical structure based on the analysis of laboratory analogue of Titan's haze with ion mobility spectrometry coupled with mass spectrometry. This robust analysis, validated with other geochemical complex mixtures, such as petroleum, allows for the observation of the size and three-dimensional structure of detected species. By comparison, with standards molecules, we exclude several structures such as pure PolyHCN and pure polycyclic aromatic hydrocarbons to be present in the principal trend of the laboratory tholins. Using theoretical calculations, we propose a plausible structure consistent with our results, which is a branched triazine-pyrazole. We observe that the larger the aerosols molecules are, the more they tend towards a structure containing small aromatics cores linked together by short chains. We suggest that the use of such an analytical approach could help advance our understanding of other complex organic compounds in the Solar System such as soluble organic matter in meteorites.

Exploring the microbial biotransformation of extraterrestrial material on nanometer scale

Exploration of microbial-meteorite redox interactions highlights the possibility of bioprocessing of extraterrestrial metal resources and reveals specific microbial fingerprints left on extraterrestrial material. In the present study, we provide our observations on a microbial-meteorite nanoscale interface of the metal respiring thermoacidophile Metallosphaera sedula. M. sedula colonizes the stony meteorite Northwest Africa 1172 (NWA 1172; an H5 ordinary chondrite) and releases free soluble metals, with Ni ions as the most solubilized. We show the redox route of Ni ions, originating from the metallic Ni° of the meteorite grains and leading to released soluble Ni2+. Nanoscale resolution ultrastructural studies of meteorite grown M. sedula coupled to electron energy loss spectroscopy (EELS) points to the redox processing of Fe-bearing meteorite material. Our investigations validate the ability of M. sedula to perform the biotransformation of meteorite minerals, unravel microbial fingerprints left on meteorite material, and provide the next step towards an understanding of meteorite biogeochemistry. Our findings will serve in defining mineralogical and morphological criteria for the identification of metal-containing microfossils.

MATERIAL OF COMETARY NUCLEI AND ASTEROIDS CAN BE STUDIED IN THE EARTH’S ORBIT

The Solar system is formed from a pri- mary gas-dust cloud. Asteroids and cometary nuclei are made of the same substance. Therefore, the study of their debris will help determine their properties. It is best to investigate the substance of meteoroids in the laboratory. The presence of radioactive chemical elements in meteor- ites provides important information about their age. The study of the isotopic composition and content of uranium and thorium gives an age of a meteorite substance of 4.6 billion years. Measurement of cosmogenic isotopes in meteorites and analysis of their content allows us to de- termine the size, mass and age of meteoritic bodies before falling to Earth. By measuring the content of tritium and helium in a meteorite, the average intensity of the cosmic rays bombarding the sample is estimated. Every day, 100- 1000 tons of meteorite material falls on the Earth’s sur- face. A large mass falls to the surface under the action of meteor showers. Meteor showers are formed from the remnants of the nuclei of known comets and asteroid bod- ies. To study the substance of the nucleus of comet Chur- yumov-Gerasimenko, a spacecraft was sent to it worth about 1 billion euros. We offer, that to study the material of some nuclei of comets and asteroids, it is possible to take meteoroid samples directly in outer space in the Earth’s orbit. There, meteoroid particles must be captured, preserved and delivered to Earth for a thorough study. To capture matter from a specific parent cometary nucleus or asteroid in outer space, traps made of silicon dioxide, which are filled with airgel, can be used. The material of the traps allows you to capture particles flying at high speed without overheating them. This allows you to save organic and other molecules in such particles. Such traps should be activated at the moments of maximums of the selected meteor showers.

Investigation of (micro-)meteoritic materials at the new hard X-ray imaging PUMA beamline for heritage sciences.

At the French synchrotron facility SOLEIL, a new X-ray imaging facility PUMA (Photons Utilisés pour les Matériaux Anciens) has been made available to scientific communities studying materials from cultural heritage. This new instrument aims to achieve 2D and 3D imaging with microscopic resolution, applying different analytical techniques including X-ray fluorescence spectroscopy (XRF), X-ray absorption spectroscopy (XAS), X-ray diffraction and phase-contrast imaging. In order to discover its capabilities a detailed analytical characterization of this beamline as an analytical and imaging tool is deemed necessary. In this work, (confocal) XRF and XAS analyses are demonstrated using the Seymchan pallasite meteorite and an Antarctic unmelted micrometeorite as case studies. The obtained spatial resolution (2 µm × 3 µm) and sensitivity (detection limits <10 p.p.m. for 1 s acquisition at 18 keV) show that PUMA is a competitive state-of-the-art beamline, providing several high-profile and high-in-demand analytical methods while maintaining applicability towards a wide range of heritage-oriented sciences.

Detection of an excessively strong 3-μm absorption near the lunar highland crater Dufay

Using the near-infrared spectral reflectance data of the Chandrayaan-1 Moon Mineralogy Mapper (M3) instrument, we report an unusually bright structure of 30 × 60 km2on the lunar equatorial farside near crater Dufay. At this location, the 3-μm absorption band feature, which is commonly ascribed to hydroxyl (OH) and/or water (H2O), at local midday is significantly (∼30%) stronger than on the surrounding surface and, surprisingly, stronger than in the illuminated polar highlands. We did not find a similar area of excessively strong 3-μm absorption anywhere else on the Moon. A possible explanation for this structure is the recent infall of meteoritic or cometary material of high OH/H2O content forming a thin layer detectable by its pronounced 3-μm band, where a small amount of the OH/H2O is adsorbed by the surface material into binding states of relatively high activation energy. Detailed analysis of this structure with next-generation spacecraft instrumentation will provide further insight into the processes that lead to the accumulation of OH/H2O in the lunar regolith surface.

H/C elemental ratio of the refractory organic matter in cometary particles of 67P/Churyumov-Gerasimenko

Context. Because comets are part of the most primitive bodies of our solar system, establishing their chemical composition and comparing them to other astrophysical bodies gives new constraints on the formation and evolution of organic matter throughout the solar system. For two years, the time-of-flight secondary ion mass spectrometer COmetary Secondary Ion Mass Analyzer (COSIMA) on board the Rosetta orbiter performed in situ analyses of the dust particles ejected from comet 67P/Churyumov-Gerasimenko (67P). Aims. The aim is to determine the H/C elemental ratio of the refractory organic component contained in cometary particles of 67P. Methods. We analyzed terrestrial and extraterrestrial calibration samples using the COSIMA ground-reference model. Exploiting these calibration samples, we provide calibration lines in both positive and negative ion registration modes. Thus, we are now able to measure the cometary H/C elemental ratio. Results. The mean H/C value is 1.04 ± 0.16 based on 33 different cometary particles. Consequently, the H/C atomic ratio is on average higher in cometary particles of 67P than in even the most primitive insoluble organic matter extracted from meteorites. Conclusions. These results imply that the refractory organic matter detected in dust particles of 67P is less unsaturated than the material in meteorites.

Thermodynamic modeling of evaporation processes of lunar and meteorite substance

A thermodynamic approach to modeling the processes of evaporation of lunar and meteorite matter is presented. Comparison of the results of model calculations and experimental data showed high accuracy of the developed approach in the description of thermodynamic properties of melts of lunar and meteorite substance and its behavior at evaporation. The observed regularities of melt evaporation are consistent with the thermodynamic values characterizing the residual melts.

Comparing analytical and numerical approaches to meteoroid orbit determination using Hayabusa telemetry

AbstractFireball networks establish the trajectories of meteoritic material passing through Earth's atmosphere, from which they can derive pre‐entry orbits. Triangulated atmospheric trajectory data require different orbit determination methods to those applied to observational data beyond the Earth's sphere of influence, such as telescopic observations of asteroids. Currently, the vast majority of fireball networks determine and publish orbital data using an analytical approach, with little flexibility to include orbital perturbations. Here, we present a novel numerical technique for determining meteoroid orbits from fireball network data and compare it to previously established methods. The re‐entry of the Hayabusa spacecraft, with its known pre‐Earth orbit, provides a unique opportunity to perform this comparison as it was observed by fireball network cameras. As initial sightings of the Hayabusa spacecraft and capsule were made at different altitudes, we are able to quantify the atmosphere's influence on the determined pre‐Earth orbit. Considering these trajectories independently, we found the orbits determined by the novel numerical approach to align closer to JAXA's telemetry in both cases. Using simulations, we determine the atmospheric perturbation to become significant at ~90 km—higher than the first observations of typical meteorite dropping events. Using further simulations, we find the most substantial differences between techniques to occur at both low entry velocities and Moon passing trajectories. These regions of comparative divergence demonstrate the need for perturbation inclusion within the chosen orbit determination algorithm.

Abundance of highly siderophile elements in lunar basalts controlled by iron sulfide melt

The Moon accreted meteoritic material towards the end of Solar System formation. Quantification of this late accretion requires an estimation of the abundance of highly siderophile, or iron-loving, elements in the lunar mantle. As lunar mantle samples are not available, estimates are derived from lunar basalt compositions, but the melting phase relations needed to derive the mantle composition are poorly constrained. Here we present sulfur solubility measurements from laboratory experiments, combined with thermodynamic calculations, which show that the lunar basalt source is likely to be saturated in a sulfur-poor, iron-rich sulfide melt that concentrates some highly siderophile elements more than others. We found that the observed range in the ratios of highly siderophile elements in primitive lunar basalts is much smaller than expected from residual sulfide control alone. Instead, the elemental ratios are consistent with mixing between primary sulfide-saturated melts and minute (<1%) amounts of lunar regolith that contain impact debris. Although the composition of some samples suggests a highly depleted lunar mantle, the exact level of depletion is unclear, because mixing trajectories overlap at the inferred level of regolith contamination. We conclude that the composition of the lunar mantle is veiled by regolith contamination of the lunar basalts. If so, highly siderophile element abundances in lunar mantle-derived materials cannot be used to determine the mass of material accreted late onto the Moon. The abundance of iron-loving elements in Moon rocks cannot indicate the amount of late accretion onto the Moon, according to experiments and thermodynamic calculations constraining the behaviour of these elements under lunar mantle conditions.

Selenium isotopes as tracers of a late volatile contribution to Earth from the outer Solar System.

The origin of Earth’s volatiles has been attributed to a late addition of meteoritic material after core-mantle differentiation. The nature and consequences of this 'late veneer' are debated, but may be traced by isotopes of the highly siderophile, or iron-loving, and volatile element selenium. Here we present high-precision selenium isotope data for mantle peridotites, from double spike and hydride generation multi-collector inductively coupled plasma mass spectrometry. These data indicate that the selenium isotopic composition of peridotites is unaffected by petrological processes, such as melt depletion and melt-rock reaction, and thus a narrow range is preserved that is representative of the silicate Earth. We show that selenium isotopes record a signature of late accretion after core formation and that this signature overlaps only with that of the CI-type carbonaceous chondrites. We conclude that these isotopic constraints indicate the late veneer originated from the outer Solar System and was of lower mass than previously estimated. Thus, we suggest a late and highly concentrated delivery of volatiles enabled Earth to become habitable.

Hydrogen molecular ions and the violent birth of the Solar System.

Many pieces of evidence indicate that the Solar System youth was marked by violent processes: among others, high fluxes of energetic particles (greater than or equal to 10 MeV) are unambiguously recorded in meteoritic material, where an overabundance of the short-lived 10Be products is measured. Several hypotheses have been proposed to explain from where these energetic particles originate, but there is no consensus yet, mostly because of the scarcity of complementary observational constraints. In general, the reconstruction of the past history of the Solar System is best obtained by simultaneously considering what we know of it and of similar systems nowadays in formation. However, when it comes to studying the presence of energetic particles in young forming stars, we encounter the classical problem of the impossibility of directly detecting them toward the emitting source (analogously to what happens to galactic cosmic rays). Yet, exploiting the fact that energetic particles, such as cosmic rays, create [Formula: see text] and that an enhanced abundance of [Formula: see text] causes dramatic changes on the overall gas chemical composition, we can indirectly estimate the flux of energetic particles. This contribution provides an overview of the search for solar-like protostars permeated by energetic particles and the discovery of a protocluster, OMC-2 FIR4, where the phenomenon is presently occurring. This article is part of a discussion meeting issue 'Advances in hydrogen molecular ions: H3+, H5+ and beyond'.

Thermodynamic Modeling of Evaporation Processes of Lunar and Meteorite Substance

The paper suggests a thermodynamic approach to modeling the evaporation of lunar and meteorite matter. Comparison of the results of model calculations and experimental data demonstrates the high accuracy of the developed approach to description of thermodynamic properties of melts of lunar and meteorite substance and its behavior at evaporation. The observed relations of melt evaporation are consistent with the thermodynamic values characterizing the residual melts.

Coupled Si and O isotope measurements of meteoritic material by laser fluorination isotope ratio mass spectrometry.

We present a procedure for the determination of the isotopic ratios of silicon and oxygen from the same aliquot of anhydrous silicate material. The sample is placed in a bromine pentafluoride atmosphere as it is heated with a CO2 laser system releasing silicon tetrafluoride and oxygen gasses. The oxygen gas is then purified to remove other reaction by-products through several liquid nitrogen traps before being captured onto a molecular sieve and transferred to an isotope ratio mass spectrometer. The silicon tetrafluoride gas is then purified using a supplementary line by repeatedly freezing to -196°C with liquid nitrogen and then thawing with an ethanol slurry at -110°C through a series of metal and Pyrex traps. The purified gas is then condensed into a Pyrex sample tube before it is transferred to an isotope ratio mass spectrometer for silicon isotope ratio measurements. This system has silicon yields of greater than 90% for pure quartz, olivine, and garnet standards and has a reproducibility of ±0.1‰ (2σ) for pure quartz for both oxygen and silicon isotope measurements. Meteoritic samples were also successfully analyzed to demonstrate this system's ability to measure the isotopic ratio composition of bulk powders with precision. This unique technique allows for the fluorination of planetary material without the need for wet chemistry. Though designed to analyze small aliquots of meteoritic material (1.5 to 3 mg), this approach can also be used to investigate refractory terrestrial samples where traditional fluorination is not suitable.

Origin of lunar fragmental matrix breccias—Highly siderophile element constraints

AbstractEjecta at North Ray crater (Apollo 16) sampled a unique section of the lunar highlands not accessible at most other landing sites and provide important constraints on the composition of late accreted materials. New data on multiple aliquots of four fragmental matrix breccias and a fragment‐laden melt breccia from this site display a variety of highly siderophile element patterns which may represent the signatures of volatile element‐depleted carbonaceous chondrite‐like material, primitive achondrite, differentiated metal, and an impactor component that cannot be related to known meteoritic material. The latter component is prevalent in these rocks besides characterized by depletions in Re and Os compared to Ir, Ru and Pt, chondritic Re/Os, and a gradual depletion of Pd and Au. The observed characteristics are more consistent with fractionations by nebular processes, like incomplete condensation or evaporation, than with lunar crustal processes, like partial melting or volatilization. The impactor signature preserved in these breccias may stem from primitive meteorites with a refractory element composition moderately different from known chondrites. The presence of distinct impactor components within the North Ray crater breccias together with observed correlations of characteristic element ratios (e.g., Re/Os, Ru/Pt, Pd/Ir) in different impact lithologies of four Apollo landing sites constrains physical mixing processes ranging from the scale of gram‐sized samples to the area covered by the Apollo missions.

2018 Nier Prize for Aki Takigawa

The Nier Prize of the Meteoritical Society recognizes early career members of the Society whose achievements extend the frontiers of meteoritics. The 2019 Nier Prize winner, Dr. Aki Takigawa, is a true scientific pioneer, who has extended meteoritics across multiple disciplinary boundaries. She began her research as an undergraduate researcher in the lab of Dr. Shogo Tachibana at the University of Tokyo in 2006. Her first project was to develop a model to explain the abundances of short-lived radionuclides in the early solar system, which not only led to a first author publication (Takigawa et al. 2008), but remains in use today (Wasserburg et al. 2017). Notably, even in this first project, she made connections with researchers in a related field, in this case astrophysicists working on supernova nucleosynthesis, so that she could draw on cross-disciplinary knowledge to make progress on an important problem in meteoritics. For her second undergraduate project, Aki worked with both Dr. Tachibana and Dr. Hiroko Nagahara. She again considered important questions about early solar system materials that link astronomy and meteoritics, this time using the effects of shape anisotropy on the infrared spectra of forsterite crystals to constrain the temperature and gas conditions of circumstellar grain condensation, similar to the presolar grain building blocks of our solar system. To complete this project, she performed laboratory experiments on the anisotropic evaporation of forsterite, measured the optical properties of the heated grains, and applied the results to the interpretation of astronomical spectra (Takigawa et al. 2009). This work ultimately became the basis of her master’s thesis, and is an important scientific milestone. The results are among the first demonstrations that the features of individual mineral grains can be used to constrain their condensation histories, providing a potential link from presolar silicates found in meteorites to the conditions of the circumstellar envelopes in which they formed (Takigawa and Tachibana 2012). For her PhD thesis also under the guidance of Dr. Tachibana, Dr. Takigawa turned from silicates to oxides, focusing on corundum, which similar to forsterite, exhibits crystal anisotropy effects in infrared spectra that can be linked to condensation conditions. This anisotropy is important for interpreting the features of some O-rich Red Giant stars, because it can explain the relative intensities of the “13-micron” and “22-micron” features as being consistent with variations in the shape of corundum grains, and thus settled a debate among astronomers about which mineral to assign the 13-micron feature (Takigawa et al. 2015). At the end of her PhD, Dr. Takigawa was awarded a Japanese Society for the Promotion of Science Ikushi Prize, one of only 20 awarded across all academic fields for the entire country in 2012. This prestigious postdoctoral fellowship provided 3 years of support, including 18 months to be spent conducting research outside Japan. Most of these 18 months were spent in Washington, D.C., working jointly at the Carnegie Institution of Washington with Drs. Larry Nittler and Conel Alexander, and in my laboratory at the Naval Research Laboratory. During that time, Dr. Takigawa expanded her work on presolar Al2O3 to include oxygen isotope measurements with secondary ion mass spectrometry, transmission electron microscopy, cathodoluminescence, and electron backscatter diffraction (Takigawa et al. 2018). Working directly with Dr. Takigawa, I was greatly impressed with her drive to learn to make each of the measurements herself, and to build a comprehensive understanding of her samples that could be used to draw broad conclusions linking cosmochemistry, astromineralogy, materials science, and astronomy. Furthermore, during her postdoctoral fellowship, she also developed a proposal for time on the newly commissioned ALMA telescope, in order to directly measure circumstellar dust features in O-rich stars that could link to her modeling and laboratory studies. Despite the intense competition for telescope time, her proposal was selected and resulted in two published papers and one in press from her observations of silicate and alumina dust (Vlemmings et al. 2017; Takigawa et al. 2017; Tachibana et al. 2019). Now an assistant professor at the Hakubi Center for Advanced Research at Kyoto University, Dr. Takigawa is a co-investigator on the NASA CAESAR mission proposal, and has begun laboratory studies looking at the interactions between amorphous silicates and cometary ice analogs. Dr. Takigawa's unique synthesis of laboratory experiments, coordinated microanalysis of meteoritic materials, astronomical observations, and modeling make her an outstanding example of the interdisciplinary nature of meteoritical science. Her results have greatly improved our understanding of the formation of refractory dust in stars and the early solar system. She has worked as an international and intellectual ambassador for the meteoritic community. It is a great honor to present her as the 2019 Nier Prize awardee.

Comparison of FT‐IR spectra of bulk and acid insoluble organic matter in chondritic meteorites: An implication for missing carbon during demineralization

AbstractPast studies of the various separable carbonaceous fractions have been unable to account for all of C in primitive chondrites. In particular, up to 20–50% of the C is lost during acid leaching of bulk samples even after the C in carbonates and soluble organic matter is accounted for. To try to better characterize the nature of this “missing C,” we have compared the bulk infrared (IR) absorption spectra of a number of primitive chondrites with those of their previously reported insoluble organic matter (IOM). The aliphatic C–H stretching bands, in particular, allow us to compare the molecular structures of bulk C with that of IOM. The spectral differences between bulk C and IOM reflect “missing C” phases that were lost during acid leaching, although we cannot completely exclude the possibility that the OM was modified after demineralization. Comparing IR spectra of bulk meteorite powder and IOM suggests that the missing C varies in its molecular structure, and that mildly thermally metamorphosed type 3 chondrites tend to be richer in an aliphatic fraction with lower CH2/CH3 ratios, relative to IOM, compared to aqueously altered carbonaceous chondrites (CI/CM/CR). The missing C is most likely released from acid‐labile functional groups, such as esters, acetals, and amides, during demineralization, although it cannot be ruled out that some fraction of the missing C is in small grains that are difficult to recover from suspension, or in water‐soluble compounds trapped in phyllosilicates.

Encyclopedia of Geochemistry

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Carbonaceous chondrite meteorites as a record of protoplanetary disk conditions

AbstractChondritic meteorites, and especially the most volatile-rich chondrites, the carbonaceous chondrites, preserve a record of the solar protoplanetary disk dust component and how it has been changed both in the disk environment itself and in its asteroidal parent body. Here we review some of the key features of carbonaceous chondrites and report some new data on their organics component. These show that the nebula reached temperature of &gt;10000C, but only very locally, to produce chondrules. Most meteoritic material underwent thermal and/or aqueous processing, but some retain delicate nebular components such as complex organic molecules and amorphous silicates.

Cosmogenic Radionuclides In Meteorites and Solar Modulation of Galactic Cosmic Rays In the Internal Heliosphere

Cosmogenic radionuclides with half-life periods T1/2 ranging from several days to a million years, produced in the nuclear reactions of galactic cosmic rays (GCR) with meteoritic matter, provide valuable information on the GCR intensity variations on a long time scale (∼1 million years) within meteorite orbits 2–4 AU from the Sun. Information on the variations of GCR gradients in the inner heliosphere was obtained by comparing the measured contents of 54Mn and 22Na in stone meteorites (chondrites) with known orbits at the time of their fall to Earth with the calculated production rates of these radionuclides in them using balloon intensity measurements of GCR (E > 100 MeV) in the stratosphere at appropriate times. Although individual gradient values show significant uncertainties, the important information is that cosmogenic radionuclides in chondrites predict low gradients (0–10% per 1 AU) for all periods of minimum solar activity in 1957–2013, according to direct measurements in interplanetary space. High gradients (50–100% per 1 AU) are predicted for periods of maximum solar activity, especially in 1992 and 2012 (up to ∼200% per 1 AU). Average values of gradients are (20 ± 10)% per 1 AU for modern solar cycles (according to the production rate of 22Na), similar to the average values for the last ∼1 million years (according to the production rate of 26Al), which indicates the constancy of the solar modulation of the GCR, at least for the last million years.