Psyche is the name of an asteroid orbiting the Sun between Mars and Jupiter and the name of a NASA space mission to visit that asteroid, led by ASU. Psyche is the first mission to a world likely made largely of metal rather than rock or ice.

The Psyche mission was chosen by NASA on January 4, 2017.

Psyche is the 14th mission selected for NASA’s Discovery Program, a series of relatively low-cost missions to solar system targets.

The asteroid Psyche may be able to tell us how Earth’s core and the cores of the other terrestrial (rocky) planets came to be. (The terrestrial planets are Mercury, Venus, Earth, and Mars.)  We can never go to the Earth’s core (see below, Why can’t we visit Earth’s core?, or read the Psyche Science page). Because we cannot see or measure Earth’s core directly, the Psyche asteroid may offer a unique window into the violent history of collisions and accretion that created the terrestrial planets. It is the only known place in our solar system where we can examine directly what may contain metal from the core of a planetesimal [18].

The core of the Earth lies at a depth of 3,000 kilometers (more than 1,800 miles). We have only drilled to 12 kilometers (about 7.5 miles) — that’s the most our technology allows today. Additionally, Earth’s core lies at about 3 million times the pressure of the atmosphere. The temperature of Earth’s core is about 5,000 Celsius (~9,000 Fahrenheit).

Visit the timeline page: https://psyche.asu.edu/timeline/

Once the mission is complete, the spacecraft will stay in orbit around (16) Psyche, like a moon. This is also how NASA’s Dawn Mission ended (read more at https://solarsystem.nasa.gov/missions/dawn/mission/toolkit/end-of-mission/)

The mission costs approximately $850 million (which includes mission development, operations, and science). This amount does not include cost for the launch service, which is procured separately. It does not include the cost for the Deep Space Optical Communications demonstration hardware or operations.

The Psyche mission science goals are to:

• Understand a previously unexplored building block of planet formation: iron cores.
• Look inside terrestrial planets, including Earth, by directly examining the interior of a differentiated body, which otherwise could not be seen.
• Explore a new type of world. For the first time, examine a world made not of rock and ice, but metal.

The Psyche mission science objectives are to:

• Determine whether Psyche is a core, or if it is unmelted material.
• Determine the relative ages of regions of Psyche’s surface.
• Determine whether small metal bodies incorporate the same light elements as are expected in the Earth’s high-pressure core.
• Determine whether Psyche was formed under conditions more oxidizing or more reducing than Earth’s core.[1]
• Characterize Psyche’s morphology.

The mission is led by Arizona State University. NASA’s Jet Propulsion Laboratory is responsible for mission management, operations and navigation. The spacecraft’s solar-electric propulsion chassis will be built by Maxar Technologies with a payload that includes an imager, magnetometer, and a gamma ray and neutron spectrometer.

To learn more about the Psyche mission, visit:

nasa.gov/psyche

psyche.asu.edu

jpl.nasa.gov/missions/psyche

Downloadable Psyche Fact Sheet

Or follow the Psyche mission on social media:

Twitter: @MissionToPsyche

Facebook: MissionToPsyche

Instagram: MissionToPsyche

Please visit https://psyche.asu.edu/get-involved/

The asteroid, Psyche, was discovered in 1852 by Italian astronomer Annibale de Gasparis. It was the 16th asteroid to be discovered, so is sometimes referred to as (16) Psyche. The asteroid was named for the goddess of the soul in ancient Greek mythology.

Psyche lies in the main asteroid belt between Mars and Jupiter.

Previously, the consensus of the science community was that asteroid (16) Psyche was almost entirely metal. New data on density, radar properties, and spectral signatures indicate that the asteroid is possibly a mixed metal and silicate world. There are still contradictions in the current available data, but the best analysis indicates that Psyche is likely made of a mixture of rock and metal, with metal comprising between 30-60% of its volume.[17]

Psyche’s chemical phase (i.e., whether the asteroid is made of metal and/or silicates) is investigated by using radar albedo and thermal inertia.

• Radar (RAdio Detection And Ranging) is “a device that sends out radio waves and picks them up again after the waves strike another object and bounce back.”[2]
• Radar albedo is the “ratio of a target’s radar cross section in a specified polarization to its projected area; hence, a measure of the target’s radar reflectivity.”[3]
• Thermal inertia “refers to the ability of a material to conduct and store heat, and in planetary science, its measure of the subsurface’s ability to store heat during the day and reradiate it during the night.”[4]

Psyche’s composition (i.e., the individual elements present on the asteroid’s surface) is investigated by examining reflectance spectra.

• Reflectance spectroscopy is “the study of light that is scattered off a surface back to your telescope and detector. Light that is scattered includes light that is reflected from a surface or refracted through a particle (or particles) and then scattered back to the detector.”[5]

We have only had good evidence for a metal-rich composition since about 2010. However, new data are being collected all the time, which we are using to continue to refine our understanding of Psyche. Current analysis suggests Psyche is likely made of a mixture of rock and metal, with metal comprising between 30-60% of its volume, but we won’t know for sure until the spacecraft arrives.[17]

Scientists think Psyche may consist largely of metal from the core of a planetesimal [18], one of the building blocks of our solar system. Psyche may be a survivor of multiple violent hit-and-run collisions, common when the solar system was forming.

A day on Psyche is about 4 hours and 12 minutes.[6] This is the sidereal rotation period, or the “amount of time it takes for a [body] to completely spin around and make one full rotation.”[7] You could live through just under six “days” on Psyche in the same time as one day on Earth!

A year on Psyche lasts about five Earth years (about 1,828 Earth days).[8]

Psyche orbits the Sun at an average distance of 3 astronomical units (AU) (about 280 million miles); Earth orbits at 1 AU (about 93 million miles). Because Psyche and Earth orbit at different speeds, the distance from Earth to Psyche varies over a large range! From < 2 AU to > 4 AU.

The mass of Psyche is estimated at (2.72 ±0.75) × 10¹⁹kg (27 sextillion!), which is about 2,700 times less massive than Earth’s moon.[6]

Mass vs. weight: Although these terms are often used interchangeably in casual settings, they do not mean the same thing. Mass is “the amount of matter in an object,” while weight is “the strength of the gravitational pull on the object; that is, how heavy it is.”[9]

A big difference between the two is that mass does not depend on gravity whereas weight does. “That’s why scientists and engineers often measure an object’s mass—how much matter the object contains—rather than its weight. Mass stays the same regardless of location and gravity. You would have the same mass on Mars or Jupiter as you do here on Earth.”[10]

Psyche is dense. Measurements are still being made; Psyche’s bulk density appears to be 3,400-4,100 kilograms per cubic meter (kg/m³) (a mix of rock and metal).[17]

The surface gravity on Psyche is much less than on Earth, and even less than on the Moon. On Psyche, lifting a car would feel as light as lifting a big dog on Earth!

Psyche mean surface gravity = 0.144 m/s².[6]

Earth = 9.8 m/s²

Moon = 1.6 m/s²

As asteroids go, Psyche is relatively large and has an irregular shape. It is 279 x 232 x 189 kilometers (173 x 144 x 117 miles).[6] If Psyche were a perfect sphere, it would have a diameter of 226 kilometers (140 miles). That is about the length of the state of Massachusetts (leaving out Cape Cod). If it were in Arizona it would stretch between Phoenix and Flagstaff! The Psyche asteroid has a surface area of about 165,800 square kilometers (approximately 64,000 square miles).[6]

Scientists have combined radar and optical observations to generate a 3D shape model of Psyche.[13] This model shows evidence for two crater-like depressions. It suggests that there is significant variation in the metal content and color of the asteroid over the surface. But remember, no one has seen the Psyche asteroid yet, so we will not know what it actually looks like until the spacecraft arrives. This is the best look we have from radar observations.

The full spacecraft, including the solar panels, is 24.76 meters (~81 feet) long by 7.34 meters (~24 feet) wide. That is about the size of a (singles) tennis court.

The bus (body) of the spacecraft is 3.1 meters (~10 feet) long by 2.4 meters (almost 8 feet) wide. To help you visualize this, it is slightly bigger than a small van; it is about the size of a garden storage shed. It is as tall as a regulation basketball hoop!

NASA has selected SpaceX of Hawthorne, California, to provide launch services for the Psyche mission. The Psyche mission will launch on a Falcon Heavy rocket from Launch Complex 39A at Kennedy Space Center in Florida.

The Psyche spacecraft will use solar-electric (low-thrust) propulsion. Solar electric propulsion uses electricity from solar arrays to create electromagnetic fields to accelerate and expel charged atoms (ions) of xenon to create a very low thrust with a very efficient use of propellant.[14] This will be the first use of Hall effect thrusters beyond lunar orbit.

View the location of the thrusters on the spacecraft:

The Psyche spacecraft is using xenon. Xenon is a gas that is in the air we breathe (in very small amounts – 0.09 parts per million![15]). Xenon gas is used in high quality light bulbs, including automobile headlamps and movie projectors. As NASA explains, “The most common propellant used in ion propulsion is xenon, which is easily ionized and has a high atomic mass, thus generating a desirable level of thrust when ions are accelerated. It also is inert and has a high storage density; therefore, it is well suited for storing on spacecraft.”[16]

From launch to arrival at the first science orbit around the asteroid, the spacecraft will travel 1,496,883,202 (~1.5 billion) miles or 2,409,000,000 (~2.4 billion) kilometers! From launch to the end of the primary mission, it will travel 2,038,718,881 (~2 billion) miles or 3,281,000,000 (~3.3 billion) kilometers!

Psyche will use an estimated 922 kilograms (7,022.46 moles) of xenon to travel 2.409 billion kilometers to Psyche. That’s 1.76 x 10¹⁸ atoms of xenon per kilometer. Or 1.76 x 10¹² atoms per millimeter traveled.

The Psyche spacecraft will carry a multispectral imager, a gamma ray and neutron spectrometer, and a magnetometer, and will conduct radio science. View the location of the instruments:

The mission is projected to deliver 620 gigabytes of data to NASA’s Planetary Data System (PDS); this is approximately the equivalent amount of storage on a standard laptop computer. In addition, we also need 450 GB for raw data and telemetry and 2,480 GB for multiple versions of PDS data products. In all, we will need 3,550 GB to support the mission.

The Psyche spacecraft includes three instruments: a magnetometer, multispectral imager, and gamma ray and neutron spectrometer. It will also use the X-band radio telecommunications system to measure Psyche’s gravity field to high precision. Data from each instrument and investigation conforms to NASA PDS4 formats, which don’t follow common formats (e.g. jpeg, pdf, etc.) but will ensure that all of the data collected is properly archived and available for generations of scientists to study.

• Provides high-resolution images using filters to discriminate between Psyche’s metallic and silicate constituents.
• Consists of a pair of identical cameras designed to acquire geologic, compositional, and topographic data.
• Purpose of the second camera is to provide redundancy for mission-critical optical navigation.
• The team is based at Arizona State University.

• Will detect, measure, and map Psyche’s elemental composition.
• Mounted on a 2-meter (6-foot) boom (“arm”) to:
  • distance the sensors from background radiation created by energetic particles interacting with the spacecraft;
  • provide an unobstructed field of view.
• The team is based at the Applied Physics Laboratory (APL) at Johns Hopkins University.

• Designed to detect and measure the remanent magnetic field of the asteroid.
• Composed of two identical high-sensitivity magnetic field sensors located at the middle and outer end of a 2-meter (6-foot) boom (“arm”).
• The team is based at Massachusetts Institute of Technology (MIT) and the Technical University of Denmark (DTU).

• The Psyche mission will use the X-band radio telecommunications system to measure Psyche’s gravity field to high precision.
• When combined with topography derived from onboard imagery, this will provide information on the interior structure of Psyche.
• The team is based at Massachusetts Institute of Technology (MIT) and the Jet Propulsion Laboratory (JPL).

• The Psyche mission will test a sophisticated new laser communication technology that encodes data in photons (rather than radio waves) to communicate between a probe in deep space and Earth.
• Using light instead of radio allows the spacecraft to communicate more data in a given amount of time.
• The DSOC team is based at the Jet Propulsion Laboratory (JPL).

  Downloadable DSOC Fact Sheet

View the location of the instruments:

The Psyche mission leadership are listed at https://psyche.asu.edu/mission/the-team/ and the full Psyche team is listed at https://psyche.asu.edu/mission/the-team/full-psyche-team/

• The PI is responsible for overall mission success and for the scientific integrity and execution of the mission within committed cost and schedule.
• The PI oversees the team organization, decides science priorities and progress, and oversees delivery of mission data to NASA’s Planetary Data System.
• The PI is the decision-maker within the Psyche team, and NASA is the ultimate decision-maker.
• The PI is responsible for ensuring that all mission participants are playing their roles as defined by the Team Guidelines.
•  Learn more by following #PI_Daily on @MissionToPsyche or on our #PI_Daily page!

The Psyche science partners are:

• Johns Hopkins University Applied Physics Laboratory (APL)
• Deutsches Zentrum für Luft- und Raumfahrt (DLR)
• Glenn Research Center (GRC)
• Jet Propulsion Laboratory (JPL)
• Lawrence Livermore National Laboratory (LLNL)
• Massachusetts Institute of Technology (MIT)
• Malin Space Science Systems (MSSS)
• Maxar Technologies
• Observatoire de la Côte d’Azur
• Planetary Science Institute (PSI)
• Smithsonian Institution
• Southwest Research Institute (SwRI)
• SpaceX
• Technical University of Denmark (DTU)
• University of Arizona
• University of California Los Angeles (UCLA)
• Yale University