World 03 · terrestrial planet
Earth
The ocean world that defines our scale.
Earth is the largest terrestrial planet and the only known world with stable surface oceans and life.
Editorial system diagram. Oceans, atmosphere and land are shown as connected conditions rather than a photographic globe.
- Order from Sun
- 3
- World type
- Terrestrial
Reference world
Habitability is a system, not a single lucky number
Earth defines the units used throughout Helios, but it should not disappear into the role of default. Liquid water, atmosphere, magnetic shielding, chemistry and energy balance work together.
Connected conditions
Oceans and air continually exchange energy
Earth's surface oceans and nitrogen-oxygen atmosphere are parts of one coupled system. Heat, water, carbon and momentum move between ocean, land, ice and air.
A global mean temperature is useful for comparison, but it cannot represent the range of climates and weather across the planet.
Baseline
Every other world is measured from here
Earth gravity, the 24-hour solar day and the Earth year are the reference units behind Helios's personal comparisons.
That familiarity is useful, but it can also hide how unusual stable surface oceans and known life are in the current planetary catalog.
Mean radius
6,371km
12,756 km equatorial diameter
Solar day
24h 00m
Prograde rotation
Temperature reference
15°C
Global surface reference, not local weather
Exploration record
How we learned to read this planet
Mission summaries are tied to dated official records and are not presented as live telemetry.
- 01
Earth-observing orbiter
Terra
Terra studies interactions among land, atmosphere, oceans and radiant energy, reinforcing the page's view of Earth as a connected system.
Reference signals
The conditions that define this world
A nitrogen-oxygen atmosphere that supports liquid surface water and life.
Atmosphere
Breathable at the surface, structured above it
Nitrogen and oxygen dominate the atmosphere, but habitability also depends on pressure, temperature, water and long-term planetary cycles.
Moon
One large natural satellite
The Moon is the single recognized natural satellite in the dated catalog and is unusually large relative to its planet.
Rings
No planetary ring system
Earth has dust and temporary particle structures in near-Earth space, but no persistent planetary rings like the giant planets.
- Axial tilt
- 23.4°
- Recognized moons
- 1 · 2026-02-12
- Rings
- Earth has no planetary ring system.
- Atmosphere
- nitrogen · oxygen · argon · carbon dioxide
Scientific limits
What these values do—and do not—describe
Reference values keep their definition, source and date context. Editorial diagrams are separated from measured planetary data.
Sources and provenance
- NASA Jet Propulsion LaboratoryPlanetary Physical Parameters ReferenceAccessed Jul 17, 2026
- NASA Jet Propulsion LaboratoryApproximate Positions of the Planets ReferenceAccessed Jul 17, 2026
- NASA SciencePlanet Sizes and Locations in Our Solar System ReferenceAccessed Jul 17, 2026
- NASA ScienceTemperatures Across Our Solar System ReferenceAccessed Jul 17, 2026
- NASA ScienceFacts About Earth ReferenceAccessed Jul 17, 2026
- NASA ScienceMoon Facts ReferenceAccessed Jul 17, 2026
- NASA ScienceTerra Latest availableAccessed Jul 18, 2026
Earth in observation
One planet, several clocks
EPIC sees the sunlit disk from DSCOVR. EONET gathers event records from contributing sources. GIBS serves dated imagery layers. Their timestamps are related, but they are not one synchronized camera.
- Capture
- Sep 17, 2026, 12:03 AM
- Color
- Natural-color composite
- Centroid
- 6.5°, 178.4°
Natural events
Read the event, then read its source
- Sea and lake iceIceberg A83open · Point · -61.27°, -51.39°Event source
- Sea and lake iceIceberg B22Fopen · Point · -67.52°, -176.03°Event source
- WildfiresWildfire Breezy, Starr, Texasopen · Point · 26.46°, -98.71°Event source
- WildfiresWildfire FLORISTON, Nevada, Californiaopen · Point · 39.39°, -120.03°Event source
- Severe stormsTyphoon Dujuanopen · Point · 31.30°, 137.90°Event source
- WildfiresPrescribed Fire RX CALV BU 104-108, Vernon, Louisianaopen · Point · 30.96°, -93.16°Event source
- WildfiresWildfire Clark, Edwards, Texasopen · Point · 29.93°, -100.35°Event source
- WildfiresWildfire Calvary Creek, Washita, Oklahomaopen · Point · 35.16°, -98.99°Event source
Earthdata layers
Curated imagery, not a layer catalogue
Terra MODIS true color
Terra / MODIS · natural
Near-real-time imagery may appear hours after observation.MODIS_Terra_CorrectedReflectance_TrueColorGOES-East fire temperature
GOES-East / ABI · analysis
Analysis layer; color represents estimated fire temperature.GOES-East_ABI_FireTempIMERG precipitation rate
GPM / IMERG · analysis
Dated precipitation analysis; not a live weather radar.IMERG_Precipitation_RateSpace environment
The Sun does not stop at the sky
DONKI records are kept as separate observations unless official activity IDs prove a relationship.
- CME · Coronal mass ejection
- CME · Coronal mass ejection
- CME · Coronal mass ejection
- CME · Coronal mass ejection
Near-Earth space
(2010 JA)
10,081,613 km miss distance
24,046 km/h relative velocity
NASA mission media
Earth, through a mission archive
Every preview comes from the reviewed NASA media list for that world. A failed request can only fall back to media curated for Earth.
Most Amazing High Definition Image of Earth - Blue Marble 2012
January 25, 2012 <b>*Updated February 2, 2012: According to Flickr, "The western hemisphere Blue Marble 2012 image has rocketed up to over 3.1 million views making it one of…
GSFCNASA media details
Earth
Behold one of the more detailed images of the Earth yet created. This Blue Marble Earth montage shown above -- created from photographs taken by the Visible/Infrared Imager…
NASANASA media details
NASA Blue Marble 2007 West
<b>RELEASE DATE: OCTOBER 9, 2007</b> <b>Credit: NASA/Goddard Space Flight Center/Reto Stöckli</b> A day’s clouds. The shape and texture of the land. The living ocean. City lights…
GSFCNASA media details