Heavy Metal

A mission to a metallic asteroid


A proposal submitted to the ESA M5 Call, 2016

Note: Following the NASA selection of the Discovery-class mission Psyche, and results of recent observations made of 16-Psyche, the science team for Heavy Metal have proposed re-targeting this mission to 216-Kleopatra.

Science Goals

Psyche's origins

  • Are metallic asteroids remnants of differentiated planetesimals?
  • What is the origin of metallic asteroids?
  • Are metallic asteroids the parent bodies of magnetized iron meteorites?

Psyche's space plasma environment

  • Is Psyche magnetized, and what is the origin of this magnetization?
  • Does Psyche have an extended magnetosphere?
  • What is the character of the space environment near Psyche?

Mission Summary


3-axis stabilised, 45 m2 solar array, launch mass 1430 kg. Carry a 6U CubeSat for insertion into low-altitude orbit around Psyche.

Launch and Transfer

Ariane 6.2, <5 years transfer using EP, possible Mars gravity assist.

Orbital Tour (1 Year)

Insertion into 5000 km circular orbit (2 months). EP transfer to 500 km circular orbit, then 300 km circular orbit. Deployment of 6U CubeSat into low orbit / controlled crash on surface EP. Transfer to elliptic and synchronous orbits (<150 km from surface). End phase may involve a controlled crash on the surface.


Optical Imager (NAC)

Wide Angle Camera (WAC)

Infrared Imager/Spectrometer (IR)

UV Spectrograph (UVS)

(Sub-)Surface Radar

Magnetometer (MAG)

Plasma Spectrometer Package

Electric field and Cold Plasma

Radio Science Experiment

Cubesat Payload

Narrow Angle Camera (NAC)

Volatile Composition Analyser (VCA)

Magnetometer (MAG)


ESA: spacecraft manufacturing, launch and operations; data archiving and distribution. PI teams: science payload and related operations and data analysis/archiving/distribution activities. All: public outreach.


Estrack, average science bitrate 1 Gbit/day, one downlink pass / week. On-board high-resolution science data make use of selective downlink.

Executive Summary

We propose a spacecraft mission to orbit and explore (16) Psyche – the largest M-class metallic asteroid in the main belt. Recent estimates of the shape, ~279×232×189 km and mass, ~2.7×1019 kg of (16) Psyche make it one of the largest and densest of asteroids, ~4.5 g cm-3, and together with the high surface radar reflectivity and the spectral data measured from Earth it is consistent with a bulk composition rich in iron-nickel. (16) Psyche orbits the Sun with semi-major axis 2.9 AU, 3º inclination, and is as yet unexplored in-situ.

The M5 mission Heavy Metal will investigate if (16) Psyche is the exposed metallic core of a planetesimal, formed early enough to melt and differentiate. High-resolution mapping of the surface in optical, IR, UV and radar wavebands, along with the determination of the shape and gravity field will be used to address the formation and subsequent evolution of (16) Psyche, determining the origin of metallic asteroids. It is conceivable that a cataclysmic collision with a second body led to the ejection of all or part of the differentiated core of the parent body. Measurements at (16) Psyche therefore provide a possibility to directly examine an iron-rich planetary core, similar to that expected at the center of all the major planets including Earth. Meanwhile, comparison with the terrestrial meteorite record will address whether metallic asteroids are the parents of magnetized iron meteorites. A short-lived dynamo producing a magnetic field early in the life of (16) Psyche could have led to a remnant field (of tens of micro Tesla) being preserved in the body today.

Like the large-scale magnetospheres of the Earth, Mercury, etc. and the induced magnetospheres of Venus and Mars, (16) Psyche is embedded in the variable flow of the solar wind. Whereas these planetary magnetospheres and induced magnetospheres are the result of intense dynamo fields and dense conductive ionospheres presenting obstacles to the solar wind, (16) Psyche may show an entirely new ‘class’ of interaction as a consequence of its lack of a significant atmosphere, the extremely high bulk electrical conductivity of the asteroid, and the possible presence of intense magnetic fields retained in iron-rich material. The small characteristic scale of (16) Psyche (~200 km) firmly places any solar wind interaction in the “sub-MHD” scale, in which kinetic plasma effects must be considered. Heavy Metal will investigate if (16) Psyche has an extended magnetosphere by mapping the local plasma density, composition, energy state and dynamics around the body, along with the magnetic field. By accurately mapping any internally retained magnetic field of (16) Psyche, we will address the origin of any magnetization (the possible remains of an early magnetic dynamo).

The possibility of remnant magnetization of the asteroid occurring only in localized regions, or otherwise being ‘disordered’ necessitates magnetic measurements close to the surface. A close approach (<100 km to the surface) with the main spacecraft is difficult due to the potentially complex gravity field and rapid rotation period of 4.2 hours of the irregular shaped asteroid. We propose instead to use a 6U CubeSat companion spacecraft to be inserted into a lower-altitude orbit for a short duration (1 month) before it makes a controlled crash toward the surface. This will facilitate near surface measurements of the magnetic field, the composition of any volatile products and produce truly high-resolution pictures of the surface, complementing the extensive measurements by the main spacecraft further away. Additionally, simultaneous measurement of the magnetic field at both the CubeSat and the main S/C will allow a detailed study of the induction of electrical currents in the asteroid surface by the solar wind. 

The Heavy Metal spacecraft will be launched from Earth with an Ariane 6.2 rocket in the time window 2029 - 2031, and by using electric propulsion, along with a possible gravity assist manoeuvre by Mars, arrive at (16) Psyche some 4 – 4.5 years later. The S/C is then planned to orbit the body for a period of 1 year, doing science operations, where after it may be sent to the surface for a controlled crash. During the nominal science operations, the main platform will orbit as close as 300-500 km from the centre of (16) Psyche

Heavy Metal will run as an ESA led mission, where the member states provide the PI led science instruments. Experienced instrument teams are already supporting this proposal, and can start the integration work during Phase A immediately upon selection and endorsement from the involved agencies. The project will follow an open data policy, with full access of the data for the science community as soon as valid calibrations are in place, though latest 6 months after being sampled. A Public Outreach Group is proposed to start their activities already in Phase A, in order to exploit fully the communication and outreach possibilities presented by this exciting science project.

While much can be learned from remote sensing of asteroids, only close (flyby, or more ideally orbital) measurements can unambiguously resolve the composition and physical character of an asteroid’s surface, mass, density, internal structure, and the many other parameters required to fully interpret the origin and subsequent evolution of the body and how it interacts with the space environment.

Heavy Metal is a mission of exploration to one of the major unexplored solar system bodies, and a potential window into conditions and processes in the early solar system, the formation of the terrestrial planets and their metal rich cores. Simultaneously, it will lead to new insights in space plasma physics and the interaction of magnetised bodies with the solar wind. The mission clearly falls within the scope of the ESA Cosmic Visions programme by addressing the major questions, “What are the conditions for planet formation and the emergence of life?” and “How does the Solar System Work?”

Participating Institutes

Swedish Institute of Space Physics (IRF), Uppsala, SE
National Institute of Astrophysics (INAF-IAPS), Roma, IT
Space and Atmospheric Physics, Imperial College London, GB
Laboratoire de Physique des Plasmas (LPP), Paris, FR
Deutches Zentrum für Luft- und Raumfahrt (DLR), Bremen, DE
Arizona State University (ASU), Arizona, US
Institut für Geophysik und extraterrestrische Physik Technische Universität Braunschweig, DE
Sapienza University of Rome Department of Mechanical and Aerospace Engineering Radio Science Lab, Roma, IT
Royal Institute of Technology (KTH), Stockholm, SE
Institute of Space Sciences (ICE, IEEC-CSIC), Barcelona, ES
Georgia Tech, Atlanta, Georgia, US
Observatoire de Paris (LESIA), Paris, FR
Tohoku University (TU), Sendai, JP
Institute of Atmospheric Physics (IAP), Prague, CZ
Bloomsburg University, Department of Environmental, Geographical, and Geological Sciences, Bloomsburg, Pennsylvania, US
Space Research Centre of the Polish Academy of Sciences (CBK), Warsaw, PL
Swedish Institute of Space Physics (IRF), Kiruna, SE
Space Research   Planetary Science Division, University of Bern, Bern, CH
Southwest Research Institute (SWRI), San-Antonio, Texas, US
Technische Universitaet Dresden, Dresden, DE
LATMOS, Guyancourt, FR
ÅAC Microtec AB, Uppsala, SE
Lviv Centre of Institute for Space Research (LCISR) of National Academy of Sciences and State Space Agency of Ukraine, Lviv, UA
Observatoire de la Côte d'Azur, TOP (Théories et Observations en Planétologie), Nice, FR
University of Bologna, Department of Industrial Engineering, Radio Science and Planetary Exploration Lab, Forlì, IT
Institute de Planetologie et d'Astrophysique de Grenoble (IPAG/PLANETO), Grenoble, FR
Mullard Space Science Laboratories (MSSL), Dorking, GB
Royal Observatory of Belgium, Bruxelles, BE
CNRS-LPC2E, Université d’Orléans, Orléans, FR
Planetary Science Institute (PSI), Tucson, Arizona, US
University of Buenos Aires, Buenos Aires, AR
University of Pisa, Department of Mathematics, Pisa, IT

Wobsite by DA, IRF-Uppsala, 2016