I can think of more than one way to get a good look at the Sun’s polar regions. After all, we’ve done it before, through the Ulysses spacecraft, which passed over the Sun’s north and south poles in 1994-1995. A gravity assist at Jupiter was the key to the mission, allowing Ulysses to arc out of the ecliptic and inward to the Sun. But Ulysses lacked the kind of remote-sensing instruments we’d like to use to compile an extensive dataset on the polar magnetic field and, as Don Hassler (SwRI) adds, “the surface/sub-surface flows” we might find in the polar regions. It’s good to see a mission designed for that purpose.

For Hassler is principal investigator on a concept that has just been approved for further study by NASA, with the haunting name Solaris. I say ‘haunting’ because it’s hard for this Stanislaw Lem reader to forget the novel of the same name, published in 1961, that explores the implications of a vast intelligence on a planet far from Earth. I realize this has been done as a film more than once and I’ve seen the films, but I leave their analysis to Centauri Dreams film critic Larry Klaes, who would know how to do justice to them. For me, the written word is the medium of choice, and this is a novel I intend to read again.

Anyway, the proposed Solaris mission is one of five science investigations just approved by NASA as part of the agency’s Medium-Class Explorer (MIDEX) program, with $1.25 million allocated for a nine-month contract for what are known as Phase A concept design studies and analyses to develop the concept. If it flies, Solaris would launch in 2025, like Ulysses using a gravity assist at Jupiter to sling it out of the ecliptic plane, flying over the solar poles at 75 degrees latitude. You might think of the surprises Cassini found at Saturn’s poles, and that odd hexagon at the north pole is still the subject of various competing hypotheses. Will we find something just as odd at the Sun? Hassler notes that we’ll at least get a good look:

“Solaris will spend more than three months over each pole of the Sun, obtaining the first continuous, high-latitude, months-long studies of the Sun’s polar regions. With focused science and a simple, elegant mission design, Solaris will also provide enabling observations for space weather research, such as the first polar views of coronal mass ejections, energetic events that spew highly magnetized plasma from the solar corona into space, causing radio and magnetic disturbances on the Earth.”

And. he adds, “It’s sure to stimulate future research through new unanticipated discoveries.”

Unexpected findings have characterized our explorations of the Solar System from the beginning, with Io and Triton being two outstanding examples, so let’s see what those solar polar regions look like. We’ll keep an eye on the progress of Solaris as it makes its way through the process. The concept calls for a Doppler magnetograph to study the polar magnetic fields and subsurface flows, along with an extreme ultraviolet instrument for polar imaging and a white light coronagraph to examine the solar corona from this perspective.

Image; Southwest Research Institute is developing the concept for a mission to study the Sun’s poles, one of the last unseen places in the solar system. This proposed solar polar NASA mission is designed to revolutionize our understanding of the Sun by addressing fundamental questions that can only be answered from a polar vantage point. Credit: Courtesy of Southwest Research Institute.

And keep an eye on another mission funded for similar Phase A concept design study, the Auroral Reconstruction CubeSwarm (ARCS), in the hands of principal investigator Kristina Lynch (Dartmouth University), a mission that would, like Solaris, be managed by SwRI. For me, the chief interest of ARCS is in its plan for 32 CubeSats and 32 ground-based observatories to work together, in this case on a study of the mechanisms driving Earth’s auroras. CubeSat designs of growing complexity are low-cost ways to fly ever more interesting missions, and the emerging notion of ‘swarm’ missions should turn out to be productive in areas as diverse as planetary imaging and extrasolar planet detection.

Meanwhile, I’m always glad to see continuing interest in missions to the Sun, given our need to understand the issues involved in close solar approaches for potential ‘sundiver’ missions deep into the gravity well for maximum acceleration to targets in the outer system. I’ll also mention Solar Cruiser as a fascinating sail design that could enable study of the Sun’s high latitudes using non-Keplerian orbits enabled by the momentum of solar photons. Principal investigator Les Johnson (MSFC) sees this as an outstanding opportunity to demonstrate the capabilities of large sails as we explore the nearest star in the cosmos.

For more on Solar Cruiser, see Heliophysics with Interstellar Implications. See also Johnson’s analysis “The Solar Cruiser Mission Concept — Enabling New Vistas for Heliophysics,” Bulletin of the American Astronomical Society, Vol. 52, No. 3 (June, 2020). Abstract.