Psyche Asteroid Mission Frequently Asked Questions What is Psyche? 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 made of metal rather than rock or ice. When was the Psyche mission selected? The Psyche mission was chosen by NASA on January 4, 2017. What kind of mission is Psyche? Psyche is the 14th mission selected for NASA’s Discovery Program, a series of relatively low-cost missions to solar system targets. What is the timeline of the Psyche mission? • 2022: Launch of Psyche spacecraft from NASA’s Kennedy Space Center, FL • 2023: Psyche spacecraft flyby of Mars • 2026: Psyche spacecraft arrives in asteroid’s orbit • 2026-2027: Psyche spacecraft orbits the Psyche asteroid for 21 months How will the Psyche spacecraft get to Psyche? 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.1 This will be the first use of Hall effect thrusters beyond lunar orbit. 1 https://www.nasa.gov/content/how-will-nasas-asteroid-redirect-mission-help-humans-reach-mars Psyche Asteroid Mission Frequently Asked Questions Last Updated 11-29-2017 What kind of propellant will the Psyche spacecraft use? 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!2). 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.”3 How big will the Psyche spacecraft be? 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. How big will the Psyche spacecraft bus (body) be? 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 Smart Car; it about the size of a garden storage shed. It is as tall as a regulation basketball hoop! How much does the Psyche mission cost? 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. When was the Psyche asteroid discovered? The asteroid, Psyche, was discovered in 1852 by 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. What is the Psyche asteroid made of? Psyche is likely made almost entirely of nickel-iron metal. Its bulk appears to be metal but its surface appears to have small areas that are rocky. 2 http://www.srh.noaa.gov/jetstream/atmos/atmos_intro.html 3 https://www.nasa.gov/centers/glenn/about/fs21grc.html Psyche Asteroid Mission Frequently Asked Questions Last Updated 11-29-2017 How do we know what the Psyche asteroid is made of? The composition of Psyche has been determined by radar albedo (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”4,5) and by thermal inertia (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.”6) When did we find out what Psyche is made of? We have only had good evidence for metal composition since about 2010. What do scientists think the Psyche asteroid is? Scientists think Psyche is the exposed nickel-iron core of an early planet, one of the building blocks of our solar system. Psyche is most likely a survivor of multiple violent hit-and-run collisions, common when the solar system was forming. What can visiting the Psyche asteroid tell us? 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. Because we cannot see or measure Earth’s core directly, the Psyche asteroid offers 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 is almost certainly a metallic core of an early planet. Why can’t we visit Earth’s core? The core of the Earth lies at a depth of 3,000 kilometers, or more than 1,800 miles. We have only drilled to 12 kilometers, or about 7.5 miles, so far because 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). 4 Ostro, S. J. (1999). Planetary Radar. Encyclopedia of the Solar System. Available from http://echo.jpl.nasa.gov/asteroids/ostro_1998_encyc_ss.pdf 5 “Radar is an acronym for ‘radio detection and ranging.’ Radar was developed to detect objects and determine their range (or position) by transmitting short bursts of microwaves. The strength and origin of "echoes" received from objects that were hit by the microwaves is then recorded. 6 https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19357 Psyche Asteroid Mission Frequently Asked Questions Last Updated 11-29-2017 Where is the Psyche asteroid? Psyche lies in the main asteroid belt between Mars and Jupiter. How long is a day on Psyche? A day on Psyche is about 4 hours and 12 minutes.7 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."8 You could live through just under six “days” on Psyche in the same time as one day on Earth! How long is a year on Psyche? A year on Psyche lasts about five Earth years (about 1,828 Earth days).9 How far is the Psyche asteroid from the Sun? 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. How dense is the Psyche asteroid? Psyche is dense--perhaps as dense as 7,000 kilograms per cubic meter (kg/m3) (similar to the density of a bar of steel).10 Does the Psyche asteroid have gravity? The surface gravity on Psyche is much less than Earth, and even less than the Moon. On Psyche, lifting a car would feel as light as lifting a dog or a 2nd grader! 7 Shepard, M. K., Richardson, J., Taylor, P. A., Rodriguez-Ford, L. A., Conrad, A., de Pater, I., ... & Close, L. M. (2017). Radar observations and shape model of asteroid 16 Psyche. Icarus, 281, 388-403: "sidereal rotation period P = 4.195948 h" 8 https://spaceplace.nasa.gov/days/en/ 9 https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=16 10 Elkins-Tanton, L. T., Asphaug, E., Bell, J. F., Bercovici, D., Bills, B. G., Binzel, R. P., ... & Jun, I. (2017, March). Asteroid (16) Psyche: Visiting a Metal World. In Lunar and Planetary Science Conference (Vol. 48). Psyche Asteroid Mission Frequently Asked Questions Last Updated 11-29-2017 How big is the Psyche asteroid? 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).11 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 641,800 square kilometers (246,300 square miles), making it just smaller than the area of the state of Texas and quite a bit larger than the area of California. What does the Psyche asteroid look like? Scientists have combined radar and optical observations to generate a 3D shape model of Psyche.12 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: What are the Psyche mission science goals? The Psyche mission science goals are to: • Understand a previously unexplored building block of planet formation: iron cores.