NASA’s Parker Solar Probe Is Being Pelted by Tiny Plasma Explosions

NASA’s Parker Solar Probe is built for extremes. It’s the fastest spacecraft they’ve ever built, and it orbits closer to the sun than any other artificial object. As it spirals inward for ever-closer views of our local star, it also encounters specs of space dust. Traveling at such incredible speeds (it reached 244,255 miles per hour on a recent pass) makes these impacts more powerful than the word “speck” would lead you to believe. In fact, NASA now says the hypervelocity dust impacts cause tiny plasma explosions that are detectable via the probe’s sensors. But don’t worry—it’s probably going to be just fine.

Parker launched in 2018 fully prepared for harsh conditions. It sports a sun shield made of a carbon-fiber-reinforced carbon composite (sometimes called reinforced carbon-carbon). The probe orients itself for each pass of the sun so the shield can keep the instruments from being roasted. Parker already has the record for closest approach to the sun, but it’s going to continue breaking that record through 2024 when it will be just 4 million miles (6.2 million kilometers) from the surface.

It’s currently rocketing around the sun at upward of 160 kilometers per second, and it’s only going to get faster. By the time it reaches that closest solar approach, Parker will be moving at nearly 200 kilometers per second—about 447,000 mph or 720,000 kph. Already, this is having consequences for the probe. While it does not have a dust detector, Parker has an electromagnetic field sensor known as FIELDS and an optical camera called WISPR. Both of these instruments have seen evidence of particles impacting at high speeds.

NASA reports that some of the hypervelocity dust impacts impart so much energy that they cause tiny plasma explosions on the surface of the probe. The dust might only be a few microns across, but the energies involved are huge at these speeds. NASA recently noted that the star tracking cameras were occasionally disrupted by these impacts. Parker needs those cameras to remain oriented correctly, so NASA started investigating. The team discovered the plasma clouds with the help of the FIELDS instrument. WISPR has also spotted some reflective debris from larger impacts on the body of the probe. While most impacts are too small to affect the probe, NASA did identify about 250 high-energy impacts.

Luckily, NASA built Parker to be robust. Hypervelocity dust isn’t enough to damage the hardware, and even slightly larger particles are unlikely to break anything upon impact. It can also maintain orientation if one of its data sources, like the star tracking cameras, temporarily drops out. Currently, NASA expects Parker to cope with the increased rate of plasma bursts as it gets closer to the sun in the next few years. Data gathered during this time could also help create better models of the environment around the sun, making future missions more predictable.

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