Hello, friends, and welcome back to This Week in Space. Hurricane season is in full swing, but this week, solar weather is not to be outdone: Twin geomagnetic storms could produce polar lights well into the middle latitudes, starting Friday night into Saturday. Let's start with some Mars news, of which there is plenty this week.
Curiosity Rover Finds Boulders Hurled By Ancient Martian Flood
Since 2014, NASA's Curiosity rover has been carefully finding its way up a ridge on Mount Sharp, the central peak in Mars' Gale Crater. The first two times the Curiosity mission team attempted to summit the ridge, the rover was turned back by sharp "gator-back" rocks and forbidding inclines. Rather than risk tipping Curiosity over and possibly losing the entire vehicle, the team looked for other routes to the top—with little success.
But it seems that the third time's the charm: finally, in August of this year, the team found an area where Curiosity could get to the ridge. There, it found boulders, flung down by an ancient Martian flood from altitudes Curiosity will never reach.
"Huge rocks were ripped out of the mountain high above, rushed downhill, and spread out into a fan below," said Curiosity team member William Dietrich in a statement. Check out the boulders in the zoomable, click-and-draggable NASA widget above.
Independent Review Finds Mars Sample Mission Is in Major Trouble
An independent review of NASA's Mars Sample Return program has concluded that the MSR mission absolutely cannot launch on time for the cost earmarked to pay for the project. And it's not even close. The very earliest the mission could launch from Earth is 2030, but the rush job would easily run $8-10 billion.
"MSR is a deep-space exploration priority for NASA," according to the review. "However, MSR was established with unrealistic budget and schedule expectations from the beginning. MSR was also organized under an unwieldy structure. As a result, there is currently no credible, congruent technical, nor properly margined schedule, cost, and technical baseline that can be accomplished with the likely available funding."
In a statement, NASA said that it is organizing a team led by Sandra Connelly, the agency's deputy associate administrator for science, to respond to the report.
Ingenuity Logs 59th Successful Flight on Mars
NASA's Ingenuity Mars helicopter just completed its 59th flight—which absolutely was not supposed to happen. Ingenuity went to Mars to show us whether powered flight was even possible in the rarefied atmosphere of Mars, but the helicopter has done better than anyone dared expect. Ingenuity's 59th flight took place on Sept. 16, Sol (Martian day) 915 for the Perseverance mission. During the flight, the rotorcraft reached a maximum altitude of 20 meters (66 feet), breaking its own previous record by an easy two meters.
Sunspot 3435 Is an Entire Problem
This week, solar cycle 25 sent not one but two extra-spicy solar flares heading our way, both from the same sunspot: number 3435. The first time 3435 exploded, it released a solar filament that reached Earth on Monday, causing a short-wave radio blackout across much of the Atlantic and sending the aurora borealis as far south as Arizona. That's par for the course for where we are in the solar cycle, less than a year from its crescendo. But then, sunspot 3435 let go again twice on Wednesday and Thursday respectively—and when it did, it released a pair of CMEs (coronal mass ejections) that have made a lot of astronomers very nervous. The reason has everything to do with their timing.
Historians believe that the Carrington event was caused by a coronal mass ejection (CME) that slammed into Earth's magnetosphere in September 1859. Two British astronomers, Richard Carrington and Richard Hodgson, recorded an ultra-bright solar flare on Sept. 1. That night, a CME from the same explosion reached Earth, creating the strongest and most destructive geomagnetic storm in recorded history.
Normally, solar filaments and CMEs take several days to make it from the Sun all the way to Earth because they don't move at anywhere close to the speed of light. But the Carrington CME took just hours to get from there to here. How? It's now thought that another solar flare, released from the same sunspot just a few days before, loosed a CME that caused its own intense aurora event on Aug. 29—and it may have "hoovered up" the dust and charged particles between the Sun and Earth, clearing the way for the Sept. 1 CME that caused the Carrington event.
So with that context in mind, and knowing that sunspots cross the solar disc from left to right as we look inward toward the Sun, here's the current sunspot map as of Friday morning. Note sunspot 3435, visible as a reddish-orange blob at center left, and the sunspots that caused the Carrington event overlaid in black.
This week's flares bear an uncomfortable resemblance, in both position and timing, to the spots that blew up back in 1859. However, with luck, these will hit us with no more than a glancing blow. The paired CMEs should hit us Saturday and Sunday, so if you possibly can, go outside and see if you can spot the aurora.
OSIRIS-REx to Drop Off Bennu Sample This Weekend
After years of traveling through deep space, NASA's OSIRIS-REx asteroid probe will fly by Earth this weekend, dropping off a sample from asteroid Bennu before it changes its name to OSIRIS-APEX and charges off for a whole different asteroid: Apophis.
Mission members have been rehearsing for this sample return mission for much of the year, because NASA intends to drop off the sample capsule in a very precise window centered on a Department of Defense test range in Utah. To get it right, nothing less than perfect split-second timing will suffice.
Happily, we don't have to catch this one on a barge, à la SpaceX with A Shortfall of Gravitas—the sample capsule will deploy a set of built-in parachutes, slowing its descent. After retrieval, NASA will share a portion of the sample with mission partners including Japan's aerospace authority, JAXA, and the Canadian Space Agency.
SpaceX May Have a Solution for Starlink Photobombs
Wednesday, SpaceX launched another batch of Starlink telecom satellites from Canaveral, powered by a reusable Falcon 9 booster (tail number B1058) on its record-setting 17th flight. Starlink satellites are expanding space-based internet access, but while they do so, their reflective surfaces are photobombing more and more telescope images of the night sky. So, Starlink announced this week that it will be adding a special optical-scatter coating to future Starlink satellites to make them reflect less light.
SpaceX says it has spent several years working on a polymer film coating that works as a Bragg mirror, taking advantage of a trick of optics to scatter light. Unlike smooth mirrors made of glass or Mylar, Bragg mirrors are made of multiple layers of plastic with varying indices of refraction. Instead of reflecting back a coherent image, Bragg mirrors produce interference that scatters visible light but still allows radio waves to pass through. (Good news for radio telescopes.) Future Starlink satellites will feature this reflective coating, as well as extra-matte black paint.
However, astronomers will have to wait for a while to see results. SpaceX designed Starlink satellites to be cheap to repair and easy to replace, but the more reflective versions currently doing all that photobombing will still be in orbit for years.
Webb Telescope Traces Europa Surface Carbon to Its Hidden Ocean
Astronomers with the Webb telescope have found clues to a carbon cycle on Europa, hidden in a bright spot on the Jovian moon's icy crust called Tara Regio—a geologically young area, recently resurfaced terrain so disrupted and jumbled that astronomers call it chaos terrain. Now we know that part of what makes it so bright is carbon dioxide ice, which the astronomers believe ultimately came from Europa's subsurface ocean.
“Previous observations from the Hubble Space Telescope show evidence for ocean-derived salt in Tara Regio,” explained Samantha Trumbo of Cornell University, lead author of a paper that appeared Thursday in Science, describing the Webb observations. “Now we’re seeing that carbon dioxide is heavily concentrated there as well. We think this implies that the carbon probably has its ultimate origin in the internal ocean.”
Skywatchers Corner
According to the European Space Agency, a Finnish legend says that the northern lights happen when the "mythical Finnish 'Firefox'" runs so quickly over the snow that its tail sends sparks flying up into the night sky. Scandinavia has a thriving aurora tourism industry, and it's easy to see why. So close to the North Pole, the aurora lights up more nights there than almost anywhere else on the planet.
True to form, an ESA partner all-sky aurora camera in Kiruna (the northernmost city in Sweden) caught this time-lapse video over about ten hours between Sept. 18-19. You guessed it: that's our sunspot friend 3435 in action.
Different colors in the polar lights come from different molecules in the atmosphere that are absorbing, then releasing, energy from the solar storm. Oxygen lights up in green at lower altitudes and red higher in the atmosphere. Nitrogen produces blue tones. Shapes in the aurora, like waves and twists, come from variations in the Earth's magnetic field.
Speaking of things that light up green in the night sky, this week is probably your last chance to see the newfound Comet C/2023 P1 Nishimura before it heads back into the silent reaches of the outer solar system for the next few centuries. Before perigee (its closest approach to Earth) last week, the comet's tails were already being buffeted and disrupted by the solar wind. This week, the comet reached perihelion (the closest it will get to the Sun). If it hasn't been entirely destroyed by solar radiation, it will be visible in the western sky after sunset next week.
