5261 Eureka
5261 Eureka is the first Mars trojan discovered. It was discovered by David H. Levy and Henry Holt at Palomar Observatory on 20 June 1990. It trails Mars (at the ) at a distance varying by only 0.3 AU during each revolution (with a secular trend superimposed, changing the distance from 1.5–1.8 AU around 1850 to 1.3–1.6 AU around 2400). Minimum distances from Earth, Venus, and Jupiter, are 0.5, 0.8, and 3.5 AU, respectively.

Long-term numerical integration shows that the orbit is stable. Kimmo A. Innanen and Seppo Mikkola note that "contrary to intuition, there is clear empirical evidence for the stability of motion around the and points of all the terrestrial planets over a timeframe of several million years".

Since the discovery of 5261 Eureka, the Minor Planet Center has recognized three other asteroids as Martian trojans: at the point, at the point, and , also at the point. At least five other asteroids in near-1:1 resonances with Mars have been discovered, but they do not exhibit trojan behavior. They are , , (36017) 1999 ND43, and (152704) 1998 SD4. Due to close orbital similarities, most of the other, smaller, members of the L5 group are hypothesized to be fragments of 5261 Eureka that were detached after it was spun up by the YORP effect (consistent with its rotational period of 2.69 h).

The infrared spectrum for 5261 Eureka is typical for an A-type asteroid, but the visual spectrum is consistent with an evolved form of achondrite called an angrite. A-class asteroids are tinted red in hue, with a moderate albedo. The asteroid is located deep within a stable Lagrangian zone of Mars, which is considered indicative of a primordial origin—meaning the asteroid has most likely been in this orbit for much of the history of the Solar System.
Q1902545
Mars trojan
Concept
Q375311
David H. Levy
PER
Q191684
Palomar Observatory
LOC
Q111
Mars
CEL
Q1811
AU
Concept
Q1763933
secular trend
UNK
Q2
Earth
CEL
Q313
Venus
CEL
Q319
Jupiter
CEL
Q753445
numerical integration
Concept
Q17350663
Kimmo A. Innanen
PER
Q7451995
Seppo Mikkola
PER
Q83021
empirical evidence
Concept
Q522039
Minor Planet Center
ORG
Q271561
resonances
UNK
None
(36017) 1999 ND43
UNK
Q665832
(152704) 1998 SD4
UNK
Q586031
YORP effect
Concept
Q11388
infrared
Concept
Q2038808
A-type asteroid
Concept
Q340587
achondrite
Concept
Q747347
angrite
Concept
Q101038
albedo
Concept
Q544
Solar System
Concept
Q155190
5261 Eureka
CEL
Q155190
5261 Eureka
CEL
Q155190
5261 Eureka
CEL
Q155190
5261 Eureka
CEL
1990-06-20T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
20 June 1990
DATE
1850-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1850
DATE
2400-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
2400
DATE
5261-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
5261
DATE
1999-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1999
DATE
1998-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1998
DATE
5261-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
5261
DATE
5261-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
5261
DATE
+5261^^http://www.w3.org/2001/XMLSchema#decimal
5261
NUMBER
+0.3^^http://www.w3.org/2001/XMLSchema#decimal
0.3
NUMBER
+1.5^^http://www.w3.org/2001/XMLSchema#decimal
1.5
NUMBER
+1.8^^http://www.w3.org/2001/XMLSchema#decimal
1.8
NUMBER
+1.3^^http://www.w3.org/2001/XMLSchema#decimal
1.3
NUMBER
+1.6^^http://www.w3.org/2001/XMLSchema#decimal
1.6
NUMBER
+0.5^^http://www.w3.org/2001/XMLSchema#decimal
0.5
NUMBER
+0.8^^http://www.w3.org/2001/XMLSchema#decimal
0.8
NUMBER
+3.5^^http://www.w3.org/2001/XMLSchema#decimal
3.5
NUMBER
-1^^http://www.w3.org/2001/XMLSchema#decimal
-1
NUMBER
+1^^http://www.w3.org/2001/XMLSchema#decimal
1
NUMBER
+36017^^http://www.w3.org/2001/XMLSchema#decimal
36017
NUMBER
+43^^http://www.w3.org/2001/XMLSchema#decimal
43
NUMBER
+152704^^http://www.w3.org/2001/XMLSchema#decimal
152704
NUMBER
+4^^http://www.w3.org/2001/XMLSchema#decimal
4
NUMBER
+5^^http://www.w3.org/2001/XMLSchema#decimal
5
NUMBER
+2.69^^http://www.w3.org/2001/XMLSchema#decimal
2.69
NUMBER
minor planet group
discoverer or inventor
site of astronomical discovery
time of discovery or invention
subclass of