Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter

A Publisher Correction to this article was published on 17 April 2019

This article has been updated

Abstract

Global dust storms on Mars are rare1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere3, primarily owing to solar heating of the dust3. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars4. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes5,6, as well as a decrease in the water column at low latitudes7,8. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H2O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals3. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Fig. 1: Evolution of dust/cloud extinction during the onset of the GDS.
Fig. 2: H2O volume mixing ratio profiles observed by ACS NIR during the onset of the GDS.
Fig. 3: H2O, HDO and D/H detections before and during the storm.

Data availability

The datasets generated by the NOMAD and ACS instruments and analysed in this study will be available in the ESA PSA repository, https://archives.esac.esa.int/psa, after the proprietary period. The datasets used directly in this study, including the data used for the figures, are available from the corresponding author upon reasonable request.

Code availability

The codes used to calculate the dust/aerosol optical depths shown in Fig. 1 are available upon request from the corresponding author. The code used to inverse the NOMAD and ACS spectra and derive density profiles has been favourably compared to the PSG tool, which can be accessed at https://psg.gsfc.nasa.gov/ and which is part of this study. A version of the retrieval code is available at https://psg.gsfc.nasa.gov/helpatm.php#retrieval.

Change history

  • 17 April 2019

    The surname of author Cathy Quantin-Nataf was misspelled ‘Quantin-Nata’ , authors Ehouarn Millour and Roland Young were missing from the ACS Science Team list, and minor changes have been made to the author and affiliation lists; see accompanying Amendment. These errors have been corrected online.

References

  1. Shirley, J. H., Newman, C., Mischna, M. & Richardson, M. Replication of the historic record of Martian global dust storm occurrence in an atmospheric general circulation model. Icarus 317, 197–208 (2019).

    ADS  Google Scholar 

  2. Montabone, L. et al. Eight-year climatology of dust optical depth on Mars. Icarus 251, 65–95 (2015).

    ADS  Google Scholar 

  3. Haberle, R. M., Clancy, R. T., Forget, F., Smith, M. D. & Zurek, R. W. The Atmosphere and Climate of Mars (Cambridge Univ. Press, Cambridge, 2017).

    Google Scholar 

  4. Daerden, F. et al. Mars atmospheric chemistry simulations with the GEM-Mars general circulation model. Icarus https://doi.org/10.1016/j.icarus.2019.02.030 (in the press).

    ADS  CAS  Google Scholar 

  5. Fedorova, A. et al. Water vapor in the middle atmosphere of Mars during the 2007 global dust storm. Icarus 300, 440–457 (2018).

    ADS  CAS  Google Scholar 

  6. Heavens, N. G. et al. Hydrogen escape from Mars enhanced by deep convection in dust storms. Nat. Astron. 2, 126–132 (2018).

    ADS  Google Scholar 

  7. Smith, M., Daerden, F., Neary, L. & Khayat, A. The climatology of carbon monoxide and interannual variation of water vapor on Mars as observed by CRISM and modeled by the GEM-Mars general circulation model. Icarus 301, 117–131 (2018).

    ADS  CAS  Google Scholar 

  8. Trokhimovskiy, A. et al. Mars’ water vapor mapping by the SPICAM IR spectrometer: five Martian years of observations. Icarus 251, 50–64 (2015).

    ADS  Google Scholar 

  9. Sanchez-Lavega, A. et al. The 2018 Martian global dust storm over the south pole studied with VMC onboard Mars Express. AGU Fall Meeting 2018, abstr. P43K-3885 (2018).

  10. Schofield, J., Kleinbohl, A., Kass, D. M. & McCleese, D. The Mars Climate Sounder – six Martian years of global atmospheric observations. In 42nd COSPAR Scientific Meeting abstr. B4.1-0002-18 (2018).

  11. Smith, M. D. THEMIS observations of Mars planet-encircling dust storm 2018a. In AGU Fall Meeting 2018 abstr. P43J-3865 (2018).

  12. Vasavada, A. Contributions of the Curiosity rover to the understanding of the Martian atmosphere. In 42nd COSPAR Scientific Meeting abstr. C3.1-0008-18 (2018).

  13. Guzewich, S., Talaat, E., Toigo, A., Waugh, D. W. & McConnochie, T. High-altitude dust layers on Mars: observations with the thermal emission spectrometer. J. Geophys. Res. Planets 118, 1177–1194 (2013).

    ADS  Google Scholar 

  14. Heavens, N. G. et al. Seasonal and diurnal variability of detached dust layers in the tropical Martian atmosphere. J. Geophys. Res. Planets 119, 1748–1774 (2014).

    ADS  Google Scholar 

  15. Määttänen, A. et al. A complete climatology of the aerosol vertical distribution on Mars from MEx/SPICAM UV solar occultations. Icarus 223, 892–941 (2013).

    ADS  Google Scholar 

  16. Wang, C. et al. Parameterization of rocket dust storms on Mars in the LMD Martian GCM: modeling details and validation. J. Geophys. Res. 123, 982–1000 (2018).

    Google Scholar 

  17. Rafkin, S. The potential importance of non-local, deep transport on the energetics, momentum, chemistry, and aerosol distributions in the atmospheres of Earth, Mars, and Titan. Planet. Space Sci. 60, 147–154 (2012).

    ADS  CAS  Google Scholar 

  18. Spiga, A., Faure, J., Madeleine, J. B., Määttänen, A. & Forget, F. Rocket dust storms and detached dust layers in the Martian atmosphere. J. Geophys. Res. 118, 746–767 (2013).

    Google Scholar 

  19. Daerden, F. et al. A solar escalator on Mars: self-lifting of dust layers by radiative heating. Geophys. Res. Lett. 42, 7319–7326 (2015).

    ADS  Google Scholar 

  20. Clancy, R. T. et al. Extension of atmospheric dust loading to high altitudes during the 2001 Mars dust storm: MGS TES limb observations. Icarus 207, 98–109 (2010).

    ADS  CAS  Google Scholar 

  21. Sefton-Nash, E. et al. Climatology and first-order composition estimates of mesospheric clouds from Mars Climate Sounder limb spectra. Icarus 222, 342–356 (2013).

    ADS  CAS  Google Scholar 

  22. McCleese, D. J. et al. Structure and dynamics of the Martian lower and middle atmosphere as observed by the Mars Climate Sounder: seasonal variations in zonal mean temperature, dust, and water ice aerosols. J. Geophys. Res. 115, E12016 (2010).

    ADS  Google Scholar 

  23. Chaffin, M. S., Deighan, J., Schneider, N. M. & Stewart, A. I. F. Elevated atmospheric escape of atomic hydrogen from Mars induced by high-altitude water. Nat. Geosci. 10, 174–178 (2017).

    ADS  CAS  Google Scholar 

  24. Forget, F. et al. Improved general circulation models of the Martian atmosphere from the surface to above 80 km. J. Geophys. Res. 104, 24155–24175 (1999).

    ADS  CAS  Google Scholar 

  25. Neary, L. & Daerden, F. The GEM-Mars general circulation model for Mars: description and evaluation. Icarus 300, 458–476 (2018).

    ADS  CAS  Google Scholar 

  26. Steele, L. et al. The seasonal cycle of water vapour on Mars from assimilation of Thermal Emission Spectrometer data. Icarus 237, 97–115 (2014).

    ADS  CAS  Google Scholar 

  27. Lewis, S. R. et al. The solsticial pause on Mars: 1. A planetary wave reanalysis. Icarus 264, 456–464 (2016).

    ADS  Google Scholar 

  28. Lammer, H. et al. Outgassing history and escape of the martian atmosphere and water inventory. Space Sci. Rev. 174, 113–154 (2013).

    ADS  CAS  Google Scholar 

  29. Encrenaz, T. et al. New measurements of D/H on Mars using EXES aboard SOFIA. Astron. Astrophys. 612, A112 (2018).

    Google Scholar 

  30. Aoki, S. et al. Seasonal variation of the HDO/H2O ratio in the atmosphere of Mars at the middle of northern spring and beginning of northern summer. Icarus 260, 7–22 (2015).

    ADS  CAS  Google Scholar 

  31. Villanueva, G. et al. Strong water isotopic anomalies in the martian atmosphere: probing current and ancient reservoirs. Science 348, 218–221 (2015).

    ADS  CAS  PubMed  Google Scholar 

  32. Webster, C. R. et al. Isotope ratios of H, C and O in CO2 and H2O of the martian atmosphere. Science 341, 260–263 (2013).

    ADS  CAS  PubMed  Google Scholar 

  33. Montmessin, F., Fouchet, T. & Forget, F. Modeling the annual cycle of HDO in the Martian atmosphere. J. Geophys. Res. 110, E03006 (2005).

    ADS  Google Scholar 

  34. Vandaele, A. C. et al. NOMAD, an integrated suite of three spectrometers for the ExoMars Trace Gas mission: technical description, science objectives and expected performance. Space Sci. Rev. 214, 80 (2018).

    ADS  Google Scholar 

  35. Neefs, E. et al. NOMAD spectrometer on the ExoMars trace gas orbiter mission: part 1—design, manufacturing and testing of the infrared channels. Appl. Opt. 54, 8494–8520 (2015).

    ADS  CAS  PubMed  Google Scholar 

  36. Patel, M. R. et al. The NOMAD spectrometer on the ExoMars Trace Gas Orbiter mission: part 2—design, manufacturing and testing of the ultraviolet and visible channel. Appl. Opt. 56, 2771–2782 (2017).

    ADS  CAS  PubMed  Google Scholar 

  37. Svedhem, H. et al. The ExoMars Trace Gas Orbiter. Space Sci. Rev. (in the press).

  38. Nevejans, D. et al. Compact high-resolution spaceborne echelle grating spectrometer with acousto-optical tunable filter based on order sorting for the infrared domain from 2.2 to 4.3 μm. Appl. Opt. 45, 5191–5206 (2006).

    ADS  PubMed  Google Scholar 

  39. Titov, D. V. et al. Venus Express: scientific goals, instrumentation and scenario of the mission. Cosm. Res. 44, 334–348 (2006).

    ADS  Google Scholar 

  40. Korablev, O. et al. The Atmospheric Chemistry Suite (ACS) of three spectrometers for the ExoMars 2016 Trace Gas Orbiter. Space Sci. Rev. 214, 7 (2018).

    ADS  Google Scholar 

  41. Korablev, O. et al. SPICAM IR acousto-optic spectrometer experiment on Mars Express. J. Geophys. Res. 111, E09S03 (2006).

    Google Scholar 

  42. Formisano, V. et al. The Planetary Fourier Spectrometer (PFS) onboard the European Mars Express mission. Planet. Space Sci. 53, 963–974 (2005).

    ADS  Google Scholar 

  43. Trompet, L. et al. Improved algorithm for the transmittance estimation of spectra obtained with SOIR/Venus Express. Appl. Opt. 55, 9275–9281 (2016).

    ADS  Google Scholar 

  44. Lemoine, F. G. et al. An improved solution of the gravity field of Mars (GMM-2B) from Mars Global Surveyor. J. Geophys. Res. 106, 23359-23376 (2001).

    ADS  Google Scholar 

  45. Millour, E. et al. The Mars Climate Database (MCD version 5.2). European Planetary Science Congress 2015, abstr. EPSC2015-43810 (2015).

  46. Villanueva, G., Smith, M., Protopasa, S., Faggi, S. & Mandell, A. M. Planetary Spectrum Generator: an accurate online radiative transfer suite for atmospheres, comets, small bodies and exoplanets. J. Quant. Spectrosc. Radiat. Transf. 217, 86–104 (2018).

    ADS  CAS  Google Scholar 

  47. Devi, V. M. et al. Line parameters for CO2- and self-broadening in the v 3 band of HD16O. J. Quant. Spectrosc. Radiat. Transf. 203, 158–174 (2017).

    ADS  CAS  Google Scholar 

  48. Devi, V. M. et al. Line parameters for CO2- and self-broadening in the v 1 band of HD16O. J. Quant. Spectrosc. Radiat. Transf. 203, 133–157 (2017).

    ADS  CAS  Google Scholar 

  49. Gordon, I. E. et al. The HITRAN2016 molecular spectroscopic database. J. Quant. Spectrosc. Radiat. Transf. 203, 3–69 (2017).

    ADS  CAS  Google Scholar 

  50. Liuzzi, G. et al. Methane on Mars: new insights into the sensitivity of CH4 with the NOMAD/ExoMars spectrometer through its first in-flight calibration. Icarus 321, 671–690 (2019).

    ADS  CAS  Google Scholar 

  51. Rodgers, C. D. Inverse Methods for Atmospheric Sounding: Theory and Practice (World Scientific, Singapore, 2000).

    MATH  Google Scholar 

  52. Maltagliati, L. et al. Annual survey of water vapor vertical distribution and water–aerosol coupling in the martian atmosphere observed by SPICAM/MEx solar occultations. Icarus 223, 942–962 (2013).

    ADS  CAS  Google Scholar 

  53. Levenberg, K. A method for the solution of certain non-linear problems in least squares. Q. J. Appl. Math. 2, 164–168 (1944).

    MathSciNet  MATH  Google Scholar 

  54. Marquardt, D. An algorithm for least-squares estimation of nonlinear parameters. J. Soc. Ind. Appl. Math. 11, 431–441 (1963).

    MathSciNet  MATH  Google Scholar 

  55. Fedorova, A. et al. Solar infrared occultation observations by SPICAM experiment on Mars-Express: simultaneous measurements of the vertical distributions of H2O, CO2 and aerosol. Icarus 200, 96–117 (2009).

    ADS  CAS  Google Scholar 

  56. Warren, S. G. & Brandt, R. E. Optical constants of ice from the ultraviolet to the microwave: a revised compilation. J. Geophys. Res. 113, D14220 (2008).

    ADS  Google Scholar 

  57. Wolff, M. J. et al. Wavelength dependence of dust aerosol single scattering albedo as observed by CRISM. J. Geophys. Res. 114, E00D04 (2009).

    Google Scholar 

  58. Fedorova, A. et al. Evidence for a bimodal size distribution for the suspended aerosol particles on Mars. Icarus 231, 239–260 (2014).

    ADS  CAS  Google Scholar 

  59. Hansen, J. E. & Travis, L. D. Light scattering in planetary atmospheres. Space Sci. Rev. 16, 527–610 (1974).

    ADS  Google Scholar 

Download references

Acknowledgements

ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-Principal Investigator teams from Spain (IAA-CSIC), Italy (INAF-IAPS) and the UK (Open University). This project acknowledges funding by the Belgian Science Policy Office (BELSPO), with financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493); by the Spanish MICINN through its Plan Nacional and by European funds under grants ESP2015-65064-C2-1-P and ESP2017-87143-R (MINECO/FEDER); by the UK Space Agency through grants ST/R005761/1, ST/P001262/1, ST/R001405/1, ST/S00145X/1, ST/R001367/1, ST/P001572/1 and ST/R001502/1; and the Italian Space Agency through grant 2018-2-HH.0. The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). This work was supported by the Belgian Fonds de la Recherche Scientifique – FNRS under grant number 30442502 (ET_HOME). The ACS experiment is led by IKI, Space Research Institute in Moscow, assisted by LATMOS in France. The project acknowledges funding by Roscosmos and CNES. The science operations of ACS are funded by Roscosmos and ESA. IKI affiliates acknowledge funding under grant number 14.W03.31.0017 and contract number 0120.0 602993 (0028-2014-0004) of the Russian government. We are grateful to all ESA ESOC, ESAC and IKI Science Operations Center personnel, whose efforts made the success of TGO possible.

Reviewer information

Nature thanks Timothy McConnochie and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information

Authors and Affiliations

Authors

Consortia

Contributions

A.C.V. and O. Korablev conceived the study, collected inputs and wrote the paper. S.A., G.V. and G.L. retrieved trace gas abundances, including those of H2O and HDO, from the NOMAD instrument. I.R.T. analysed the SO solar occultation data. L.T. provided transmittances from the NOMAD SO v0.3a. J.T.E. and S.R. provided and analysed the data used as input for the retrieval method and initial global circulation model (GCM) fields. F.D. and L.N. provided the GCM fields. S.V., F.G.-G., F.L., S.L. and J.K. provided the GCM background and discussion. F.A., O. Karatekin and V.W. coordinated the dust observations between the infrared and ultraviolet regions, and nadir and occultation. M.L.-V., J.-C.G, M.G.-C., M.L.-P. and B.F. analysed the NOMAD limb data. M.L.-P. provided the dust profiles from the NOMAD infrared channel. M.D.S., R.T.C. and M.J.W. provided contextual information from the Themis/Mars Orbiter instrument. M.G. provided contextual information from PFS/Mars Express. M.J.M. provided support for the spectroscopic parameters selection. F.S. and N.A.T. provided alternative methods to derive trace gases from the NOMAD infrared channel. J.W. and E.C. provided support for the selection of the surface properties. A.M. gave support for the calibration of the infrared channels. C.D., D. Bolsée and Y.W. were involved in the UVIS calibration and data pipeline. B.R. and E.N. designed the NOMAD observations, helped by J.M. for the UVIS channel. A.A.F. calibrated the ACS NIR data and analysed the water profiles assisted by F.M., A.T., D. Betsis and J.-L.B. CO2 data were analysed by D.A.B. The datasets for ACS NIR were prepared by A.T. and A.P., and N.I.I., A.S. and I.M. prepared the TIRVIM dataset. A.T. and A.V.G. designed the ACS observations. M.L. and D.P. analysed the TIRVIM occultation profiles. K.S.O., J.A. and L.B. provided support for the water retrieval. Y.S.I. helped in the MIR calibration. M.R.P., G.B. and J.-J.L.-M. provided support in the selection of the NOMAD observations based on scientific interest. F.F., C.F.W., D.R., J.L.V. and H.S. coordinated the observations of the various instruments on TGO. All authors assisted A.C.V. and O. Korablev with the preparation of the manuscript.

Corresponding author

Correspondence to Ann Carine Vandaele.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Continuum optical depth versus latitude and solar longitude.

The colour denotes the lowest altitude at which the optical depth is less than 1.0, that is, the lowest altitude where sunlight can still penetrate the atmosphere easily. There is a strong latitudinal dependence, with northern and southern high latitudes being relatively clear until the line of sight drops below 10–15 km (blue and dark blue)—except during the Ls = 200°–240° period, where the GDS appears to have raised this altitude to 20–25 km (light blue and cyan).

Extended Data Fig. 2 Impact of the dust storm on NOMAD LNO nadir observations.

a, b, The calibrated radiance at 2.3 μm is shown for two orbits, before (a) and during (b) the dust event, as a function of the latitude. Red lines show the results of a radiative-transfer model. The dust opacity before the GDS is τ = 0.46 at 3 μm, whereas during the event there is an increase by at least a factor of 10 (τ = 4.6). The 1σ error of the data is 8.2 × 10−5 W m−2 sr−1 cm. c, Surface albedo. Black, albedo at 2.33 μm from the OMEGA/Mars Express instrument (corresponding to NOMAD order 190); red, bond albedo from the TES/Mars Global Surveyor instrument, scaled to the OMEGA one.

Extended Data Fig. 3 Atmospheric transmittances measured by NOMAD during the storm.

Data obtained at Ls = 196.64°, latitude 51° N and longitude 148° E, showing HDO absorption features (arrows) appearing at tangent heights of up to 50 km; most of the other absorption features originate from CO2. The transmittances have been normalized by the continuum defined by a fifth-order polynomial applied to eliminate aerosol extinction and instrument effects. The transmittances are plotted with an interval of 0.015 to avoid overlapping.

Source data

Extended Data Fig. 4 Example of NOMAD water-retrieval results.

Top, transmittance measured at a tangent height of 22.2 km (black), best fit (blue) and different simulations with 1 p.p.m. (cyan) and 100 p.p.m. (green) water content. The insets show zooms on two absorption lines of water. Bottom, residuals between the observation and the best fit. The transmittance errors were calculated from the 1σ noise value.

Extended Data Fig. 5 Example of ACS NIR water-retrieval results.

Top, transmittance measured at a tangent height of 34.1 km (black), best fit (blue) and different simulations with no water (cyan), 1 p.p.m. (red) and 50 p.p.m. (green) water content. The insets show zooms on several absorption lines of water. Bottom, residuals between the observation and the best fit. The transmittance errors were calculated from the 1σ noise value.

Extended Data Fig. 6 Extinction of water ice measured by NOMAD.

Results shown as a function of particle size (retrieved effective radius, reff; top) and slant optical depth (in units of km−1; bottom). Data obtained for the solar occultation before the dust storm, on 7 May between 05:40 and 05:46 utc (local time 18:00), which covers the latitude range 44° N to 57° N and the longitude range −122.6° E to −121.4° E.

Source data

Extended Data Fig. 7 Independent retrieval of dust and water ice from the TIRVIM dataset.

Data obtained for a typical southern-hemisphere occultation (20 June 2018; latitude (Lat) 81° N; longitude (Lon) −66° E; egress). Shown is a selection of transmission profiles at five wavelengths (left), the corresponding slant opacities (top centre) and extinction profiles (top right), the retrieved effective radius reff (in micrometres; bottom centre) and the aerosol number density (in cm−3; bottom right). The occultation measurement was performed at orbit 2556 (local time 21:25) and covers the latitude range 81° N to 82° N and the longitude range −67° E to −60° E. The observation corresponds to the ACS MIR H2O and HDO profiles shown in Fig. 3 (yellow curves). The water ice and dust are well distinguished using the 3-µm water-ice absorption band (wavenumber 3,263 cm−1 in the figure). In this case the water-ice cloud is detected at 25–30 km. All errors shown are 1σ.

Extended Data Table 1 Overview of NOMAD and ACS observations of H2O and HDO used in this study

Source data

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Vandaele, A.C., Korablev, O., Daerden, F. et al. Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter. Nature 568, 521–525 (2019). https://doi.org/10.1038/s41586-019-1097-3

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41586-019-1097-3

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing