Mercury
Mercury's orbit is the most eccentric of all the major planets, leading to this orbital characteristic, where its solar day is longer than its year.
What is a 3:2 spin-orbit resonance?
Venus has a thick atmosphere primarily composed of this greenhouse gas, contributing to surface temperatures hot enough to melt lead.
What is carbon dioxide?
These two moons of Mars are believed to be captured asteroids due to their irregular shapes and small sizes.
What are Phobos and Deimos?
This moon of Mars is closer to the planet and orbits it in less than 8 hours.
What is Phobos?
This NASA mission orbited Mercury from 2011 to 2015, mapping its surface and analyzing its composition.
What is MESSENGER?
This vast impact basin, over 1,500 km across, likely formed from a massive collision during the late heavy bombardment.
What is the Caloris Basin?
Despite its similar size to Earth, Venus has surface pressure approximately this many times greater than Earth’s.
What is 90 times greater?
This massive volcano on Mars is the tallest planetary mountain in the solar system.
What is Olympus Mons?
Phobos and Deimos are thought to be captured objects from this population of small solar system bodies.
What are asteroids (or the asteroid belt)?
This pair of rovers landed on opposite sides of Mars in 2004 to study its geology and search for signs of past water.
Which are Spirit and Opportunity?
Mercury’s high density suggests it has an unusually large one of these, which makes up about 85% of its planetary radius.
What is an iron core?
Venus has extensive volcanic plains and features like pancake domes, indicating it may still be this geologic type of planet.
What is volcanically active?
Despite its reddish hue, Mars’ thin atmosphere is composed of about 95% this gas.
What is carbon dioxide?
Unlike most moons, Phobos orbits Mars at such a low altitude that it’s gradually doing this over time.
What is spiraling inward (or getting closer to Mars)?
This Soviet space program successfully landed multiple probes on Venus and returned the first color images from the surface.
What is the Venera program?
Unlike Venus and Mars, Mercury possesses this planetary feature, which could be generated by a partially molten core or be a remnant from the past.
What is a global magnetic field?
The upper clouds of Venus are composed largely of droplets of this highly corrosive substance.
What is sulfuric acid?
Evidence from orbiters and rovers suggests this phase of water may exist temporarily just below the Martian surface.
What is liquid water?
Both Phobos and Deimos are significantly smaller than Earth’s Moon. This is the approximate maximum diameter of Deimos.
What is 15 kilometers?
Launched in 2003, this ESA orbiter has been key in mapping the Martian surface and analyzing its atmosphere.
What is Mars Express?
Despite being the closest planet to the Sun, Mercury can drop to -180°C at night due to this.
What is a lack of a substantial atmosphere?
Though often called Earth’s twin, Venus lacks this geologic process that plays a key role in Earth’s carbon cycle and plate movement.
What is plate tectonics?
Mars takes about this many Earth days to complete one orbit around the Sun.
What is 687 days?
Deimos has a smoother appearance than Phobos due to this process, in which fine dust fills in surface features over time.
What is regolith accumulation?
In 2021, this NASA rover landed in Jezero Crater to search for signs of ancient life and collect samples.
What is Perseverance?