There Were Glaciers… on Mercury?

A view of Mercury’s north polar chaotic terrain (Borealis Chaos) and the Raditladi and Eminescu craters where evidence of possible glaciers has been identified. Red areas identified regions of potential salt glaciers
A view of Mercury’s north polar chaotic terrain (Borealis Chaos) and the Raditladi and Eminescu craters where evidence of possible glaciers has been identified (Credit: NASA)

I have lost count of how many times I have given public lectures and explained the temperature differences between Mercury and Venus. How Mercury, surprisingly isn’t the hottest planet in the Solar System and how that badge goes to Venus, thick atmosphere blah blah blah.  Mercury and its complex surface geology does of course get a good chunk of time but a recent paper has rather caught my attention and turned what I thought I knew about Mercury on its head! In short, a team of scientists have announced evidence for salt glaciers on Mercury!

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The Solar Wind Whistles as it Passes Mercury

Image of chorus wave generation on Mercury. Credit: NASA/JHUAPL/Carnegie Institution of Washington

Mercury is the closest planet to our Sun, ranging from 46 million km (28.58 million mi) at perihelion to 69.82 million km (43.38 million mi) at aphelion. Because of its proximity, Mercury is strongly influenced by the steam of plasma constantly flowing from the Sun to the edge of the Solar System (aka. solar wind). Beginning with the Mariner 10 mission in 1974, robotic explorers have been sent to Mercury to measure how solar wind interacts with Mercury’s magnetic field to produce whistler-mode chorus waves – natural radio emissions that play a key role in electron acceleration in planetary magnetospheres.

In addition to being the cause of geomagnetic storms and auroras in planetary atmospheres, these waves also lead to electromagnetic vibrations at the same frequencies as sound, producing chirps and whistles. In a recent study, an international research team consulted data from the BepiColombo International Mercury Exploration Project, which gathered data on Mercury’s magnetosphere during its first and second flyby. Their results are the first direct probing of chorus waves in Mercury’s dawn sector, which showed evidence of possible background variations in magnetic field.

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BepiColumbo Makes its Third Flyby of Mercury, Seeing the Planet's Night Side

Several geological features are visible in this image of Mercury taken by the ESA/JAXA BepiColombo mission on June 19, 2023 as the spacecraft sped by for its third of three gravity assist maneuvers at the planet. Credit: ESA/BepiColumbo/MTM.

ESA’s BepiColumbo continues its journey to Mercury by making another flyby … of Mercury! This is the third of six planned flybys of its destination planet, each of which gives the spacecraft a gravitational deceleration. Eventually, it’ll slow down enough to go into its final operational orbit.

In the most recent flyby on June 19, 2023, the spacecraft sped past the planet’s night side and took a series of images from 236 km (145 miles) above Mercury’s surface. From these 217 images, the BepiColumbo team created a movie of the flyby, which includes a 3D scene.

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Astronomers Come Closer to Understanding How Mercury Formed

Artist's concept of the MESSENGER spacecraft on approach to Mercury. Credit: NASA/JPL

Simulations of the formation of the solar system have been largely successful. They are able to replicate the positions of all the major planets along with their orbital parameters. But current simulations have an extreme amount of difficulty getting the masses of the four terrestrial planets right, especially Mercury. A new study suggests that we need to pay more attention to the giant planets in order to understand the evolution of the smaller ones.

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Two “Super Mercury” Exoplanets Found in a Single System

Mercury gives a clue to Super-Mercuries
Astronomers have found a star system with two planets like Mercury, but bigger. Our own Mercury could supply clues to their composition and formation. (Credit: NASA/Johns Hopkins University/Applied Physics Laboratory.Carnegie Institution of Washington).

There’s a star system out there with three super-Earth planets and two super-Mercuries. Super-Earths are fairly familiar types of exoplanets, but super-Mercuries are rare. Those are planets with the same composition as our own Mercury, but larger and denser. Yet, here’s HD 23472, showing off two of eight known super-Mercuries in the galaxy.

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BepiColombo Meets Mercury for the First Time on October 1

New research suggests that Mercury is still contracting and shrinking. Credits: NASA/JHUAPL/Carnegie Institution of Washington/USGS/Arizona State University

BepiColombo made a quick visit to Venus in August and is on to its next rendezvous. On October 1st it’ll perform a flyby of Mercury, the spacecraft’s eventual destination. This visit is just a little flirtation—one of six—ahead of its eventual orbital link-up with Mercury in late 2025.

The quick visit will yield some scientific results, though, and they’ll be just a taste of what’s ahead in BepiColumbo’s one-year mission to Mercury.

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It’s Time to Send a Lander to Mercury

So much in the astronomy community revolves around the decadal survey.  Teams of dozens of scientists put hundreds of hours developing proposals that eventually try to impact the recommendations of the survey panel that influence billions of dollars in research funding over the following decade.  And right now is the prime time to get those proposals in.  One of the most ambitious is sponsored by a team led by researchers at John Hopkins University Applied Physics Laboratory (APL).  Their suggestion – it’s time to land on Mercury.

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Who was Giuseppe ‘Bepi’ Colombo and why Does he Have a Spacecraft Named After him?

Astronomers have an excellent habit of naming large projects after deserving contributors to their field.  From Nancy Grace Roman to Edwin Hubble, some of the biggest missions are named after space exploration pioneers. When ESA and JAXA sat down to figure out a name for their new Mercury probe, they would have come across an important name early in their research – Giuseppe “Bepi” Colombo – the man who helped plan the Mariner 10 Mercury mission.

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