A Weak Magnetic Field
The Mariner 10 spacecraft perceived the magnetic field of Mercury and its magnetosphere in March of 1974 and again in March of 1975.
The spacecraft discovered the field’s strength to be 1.1% that of Earth’s magnetic field. When Messenger was introduced to Mercury back in 2004, we found that Mercury’s magnetic field might have once been much more powerful than it is now.
What happened to change this? No one knows.
Mercury Has a “Tail”
Mercury’s gravity is too fragile to hold a thick or permanent atmosphere.
When atoms steam from the planet’s exterior due to solar photons or other methods, some of these atoms create a trail that leads away from the sun.
A Day on Mercury
A single day on Mercury lasts about 58 Earth days.
Due to its quick orbital speed and delayed sidereal rotation, the time it takes the sun to retreat to the same position in the sky is truly 176 Earth days.