This weekend, I attended a special event at NASA’s Jet Propulsion Laboratories in Pasadena, CA to celebrate the Juno spacecraft’s July 4th arrival at the planet Jupiter. Planetary scientists study outer space, while neuroscientists such as myself study inner space. But as my visit to JPL revealed, the goals and challenges of each discipline are far more similar than you might think. So, what is Juno, and how does its mission mirror that of many neuroscientists?
Albert Einstein once famously said, “God does not play dice.” But for the ancient Romans, the gods were far more mischievous. Jupiter, perusing an affair with the nymph Io from Argo, did what any guilty deity would do. The king of the gods created a thick cover of clouds to hide the affair from his wife, Juno, atop Mt. Olympus. Alas, Juno still saw through the clouds, exposing Jupiter’s secrets.
For Roman deities, seeing through opaque objects is child’s play. But for scientists, the limitations of the eyes severely limit what we can learn about the inside of our bodies and the interiors of planets. Just as seeing the brain through the skull is a challenge for neuroscientists, seeing the interior of a planet through its atmosphere is a challenge for planetary scientists. Although Jupiter lacks a solid surface, its thick cloud layers hide a core and mantle that offer clues to how planets form. Juno — a clever acronym for JUpitter Near-polar Orbiter — will follow the eponymous goddess of Roman mythology by “seeing” through Jupiter’s clouds to expose the giant planet’s inner secrets.
While rocket science isn’t brain surgery, the tools Juno uses to see inside Jupiter are surprisingly similar to the tools used by neuroscientists to see inside the brain. Mounted on one of Juno’s three solar panels is a special tool for measuring magnetic field strength, a magnetometer, not unlike those found in the helmet of an MEG machine that measures magnetic brain activity. The probe will also use radio antennas to listen to Jupiter’s radio emissions. Similarly, radio antennas inside magnetic resonance imaging (MRI) machines are critical for imaging the brain. And just as neuroscientists use NIRS (Near-InfraRed Spectroscopy) to observe brain tissue using oxygen, the near-infrared spectrometer aboard Juno will observe the stunning Jovian auroras.
Central to these technologies is electromagnetic radiation. The light visible to our eyes and most cameras is just a thin sliver of the electromagnetic spectrum that also includes radio, infrared, ultraviolet, X-rays, and gamma rays. The ability of X-rays to “see” through solid matter was discovered by German engineer and physicist Wilhelm Röntgen, whose wife, on seeing an X-ray image of her hand, exclaimed, “I have seen my own death!” Although X-rays are used to create CT scans of the brain, their high energy can damage DNA. Unlike X-rays, radio waves used in MRI are a form of non-ionizing radiation that does not pose a risk of cancer. An MRI machine forms a picture of different tissues in the body by exciting the spinning hydrogen nuclei in these tissues and listening to the radio signatures of different tissues — white matter, gray matter, cerebral spinal fluid — as the hydrogen nuclei slowly relax. By the same token, Juno’s antenna will listen to Jovian radio emissions that offer insights into its internal composition. These strange emissions have a haunting complexity, as revealed by the two Voyager spacecraft that eavesdropped on Jupiter almost forty years ago.
Inside Jupiter, an exotic form of matter known as metallic hydrogen allows electric currents to flow effortlessly, generating a gargantuan magnetic field around the planet. Juno’s sensitive measurements of this field will yield new insights into Jupiter’s mantle of metallic hydrogen. As strange as it may sound, far weaker electric currents inside your brain generate a neuromagnetic field around your head! Though unimaginably weaker than Jupiter or Earth’s magnetic field, a sensitive technique called magnetoencephalography, or MEG, allows neuroscientists to study the feeble neuromagnetic field and gain insights into brain function. Because the brain’s magnetism is overwhelmed by stronger magnetic fields in the environment, the technical feat accomplished by MEG has been compared to hearing a pin drop at a rock concert.
The challenges faced by studying brains and studying planets may be two sides of the same coin. But what about their goals? The neuroscientist’s ultimate endeavor is to use the secrets of the brain to achieve a complete understanding of the mind and the human condition. Planetary scientists follow a similar endeavor of studying the solar system’s secrets to achieve a complete understanding of humanity’s place in the cosmos. Why are we here and how did we get here? In recent years, many planets similar to Jupiter have been discovered orbiting harrowingly close to other stars, so close that a year on such a world would last only a few hours. These discoveries have forced scientists to question existing theories of planet formation. By studying the composition of our solar system’s archetypical gas giant, the Juno team hopes to advance our understanding of how worlds form around distant suns. Where there are other worlds, there may be other life. And where there is other life, there may be other brains and minds like our own.