by Theodore R Frimet
The March of the Monkeys
Cassini crashed the party
After writing the Void, I came to the conclusion that it did not service the mindset of the Amateur Astronomy community, one IOTA. So be it my surprise when I decided to catch up with a couple of issues of Science, the journal from AAAS, and read about Saturn. The introductory article written by Keith T. Smith (1) was inspiring to help me focus on a few of my favorite things. Smith composes a thought list on the magnetic field, an inner radiation belt, solid grains falling from the rings to the planet, and Saturns atmospheric composition.
How amazing is it to find out, that during the course of self study, with dingy little sensors and an Arduino, that the budding Amateur may have some working knowledge of how a magnetometer might be employed. Cassini was no shrinking violet, here. Her fluxgate magnetometer measured Saturn’s magnetic field, with fierce resolution. In cooperation with her onboard star cameras and gyroscopes, a vector analysis inferred the magnetic field structure. We confirmed the north-south asymmetry of Saturns magnetic field. The implication of author M.K. Dougherty (2) are the presence of strong zonal flows. All signs express a growing knowledge of the planets deep dynamo.
Nothing like a good cup of coffee to wake you up, on a chilly November morning! And like the best of latte tasters – know that Saturn and her rings gets a daily dose of energetic protons, located between the planets surface, and her rings. Despite the inner radiation belt, being limited by the atmosphere, an astounding measurement of proton energy is demonstrated and bounded by 25 MeV to the giga-electron volt range (3). A reduced intensity, within the inner area, attributes itself to the presence of ring dust. Matter always seems to get in the way! To me, it would appear that having knowledge of energetic protons, we have a new utility to measure what could be the waxing and waning of inner belt stability. Just my 2 cents.
L. Lamy (4) introduces us to the sounds of Saturn. It is reminiscent of using a radio receiver to listen to Jovial sounds. However, here, we are briefed on the necessity to have close proximity to make accurate measurement, to understand how low-frequency radiation is generated. And Cassini had arrived to be on site, to do just that! Sampling the 10 to 20 kHz bandwidth, a correlation to coincident ultraviolet (UV) auroral oval was accomplished while observations were made by the Hubble Space Telescope. The main conclusion reached was that low frequency emissions are strongly time variable. Perhaps the next time we probe Saturn, with a bent on UV, we could “tune in” to the low frequency source to accompany the imaging?
Manna from Heaven. Ring Rain! How more eloquent to say that there are grains of dust falling, from the rings of Saturn, into her atmosphere? H.-W. Hsu (5) introduces us, to the grand finale mission of 2017. The 22 transits between this planet and her innermost D ring had us analyzing the dust. The tool employed is called the cosmic dust analyzer. The estimate is “a few tons of nanometer sized ejecta is produced each second across the main rings”. (ibid) Wonders of wonders that science is, we are told that the two grain types are known as water ice and silicate. Having confirmed the constituents of Ring Rain, we continue to be left with educated guesses on the ring erosion process. However, the ratio of dust grains does vary 1:11 to 1:2 with latitude. Between the ejecta velocity, and the offset magnetic fields, it encourages me to hunt for a visual on the phenomenon.
At my last public outreach for the year, for our parent organization, UACNJ, a question was posed on how we know the composition of exoplanetary atmospheres. I quickly summarized for our guest. We initially detected “wobble” as a Jupiter sized planet passed in front of her main star. And that as the light passed thru this hot Jupiter, we could measure the spectrum of light. From this measurement, it provides us clues as to the inherent chemical composition of the exo-planets atmosphere. Herein, though, J.H. Waite (6), reminds us that we study Saturn’s atmosphere, in situ! We learn that the primary tool for this job is called the Cassini Ion Neutral Mass Spectrometer (INMS). It took measurements of the upper atmosphere, and within the rings. The INMS detected an abundance of Hydrogen (H2) at all altitudes. Methane, ammonia, molecular nitrogen, carbon monoxide, and carbon dioxide were all observed along with water from the rings. Fragments from organic nanoparticles were observed. The impact of any organic material probably denigrated upon collection within the INMS chamber. Hence, only organic fragments were recorded due to high velocity impact. Cassini was no slouch, as she vaulted through her mission end at a velocity in the neighborhood of 31 km s-1. Evidence abounds pointing to a molecular soup of volatiles and organic fragments. It doesn’t take a leap of faith, to suggest that the chemistry of Saturns rings doesn’t stay localized, and contributes to the chemistry of the planets atmosphere.
We dove off the deep end, within the rings of Saturn, and crashed into her veiled atmosphere. All for the mix of scientific measurement, discovery and to maintain an even keel on Planetary Protection. There is, of course, much data that needs to be gone through. Perhaps we as Amateurs can stay abreast of the developments, as Cassini’s last dive, continues to present to us a treasure trove of information on Saturn.
- Smith, K. T. (2018). Diving within saturn’s rings. Science, 362(6410), 44-45.
- M.K. Dougherty et al., Science 362 eaat5434 (2018). DOI 10.1126/science.aat5434
- E. Rousssos et al., Science 362, eeat1962 (2018). DOI 10.1126/science.aat1962
- L. Lamu et al., Science 362, eaat2027 (2018). DOI: 10.1126/science.aat2027
- H.-W. Hsu et al., Science 362, eaat3185 (2018). DOI: 10.1126/science.aat3185
- J.H. Waite Jr. et al., Science 362, eaat2382 (2018). DOI: 10.1126/science.aat2382