Pytheas is a small lunar

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 impact crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 located on the southern part of the Mare Imbrium

Mare Imbrium

Mare Imbrium, Latin for "Sea of Showers" or "Sea of Rains", is a vast lunar mare filling a basin on Earth's Moon and one of the larger craters in the Solar System. Mare Imbrium was created when lava flooded the giant crater formed when a very large object hit the Moon long ago...

, to the south of the crater Lambert

Lambert (lunar crater)

Lambert is a lunar impact crater on the southern half of the Mare Imbrium basin. It lies to the east and somewhat south of the slightly larger crater Timocharis. To the south is the smaller Pytheas, and some distance to the west-southwest is Euler....

.

It has a sharply defined rim, a hummocky outer rampart, and an irregular interior due to slumping or fall-back. There is a small crater along the northern outer rampart, and a similar crater about 20 km to the west. The crater possesses a small ray system

Ray system

A ray system comprises radial streaks of fine ejecta thrown out during the formation of an impact crater, looking a bit like many thin spokes coming from the hub of a wheel. The rays can extend for lengths up to several times the diameter of their originating crater, and are often accompanied by...

 that extends for a radius of about 50 kilometers. It is surrounded by lunar mare that is dusted with ray material from Copernicus

Copernicus (lunar crater)

Copernicus is a prominent lunar impact crater named after the astronomer Nicolaus Copernicus, located in eastern Oceanus Procellarum. It is estimated to be about 800 million years old, and typifies craters that formed during the Copernican period in that it has a prominent ray system.-...

to the south.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Pytheas.

Pytheas	Latitude	Longitude	Diameter
A	20.5° N	21.7° W	6 km
B	17.5° N	19.4° W	4 km
C	18.8° N	19.1° W	4 km
D	21.1° N	20.5° W	5 km
E	18.1° N	19.0° W	4 km
F	16.5° N	19.1° W	5 km
G	21.6° N	17.7° W	4 km
H	20.5° N	16.5° W	3 km
J	21.6° N	21.1° W	3 km
K	19.9° N	16.2° W	2 km
L	18.6° N	16.9° W	3 km
M	19.9° N	17.7° W	3 km
N	22.5° N	20.5° W	3 km
U	21.7° N	19.4° W	3 km
W	21.7° N	23.7° W	3 km