Educational only — not for clinical decisions
These tools illustrate published standards and research. They are simplified, unvalidated and not reviewed. Do not use them to diagnose, treat, clear anyone to fly, or plan real operations. All calculations run in your browser; nothing you enter is stored or sent.
Earth–Moon and Earth–Mars Communication Delay Calculator
Also: Mars signal delay · light time to Mars · telemedicine delay
Distance from EarthBehavioral Health & SleepIn-flightCislunar / Lunar orbitLunar surfaceMars transit & surfaceClinicianPublicStudentOperator / Spaceflight participantAstronaut & candidate
- Signal delay is distance ÷ speed of light: about 1.3 seconds one way to the Moon, and from a few minutes up to about 22 minutes to Mars depending on where the planets are (NASA: longest delays about 21–23 minutes) [1][2][3]. ◆◆◆◆ High · E
- Around solar conjunction (about every 26 months) the Sun can block Earth–Mars communication for weeks [1]. ◆◆◆◆ High · E
- At Mars, real-time telemedicine is impossible; crews must manage emergencies on their own.
Proposed certainty (◆ High → ◇ Very low) and evidence-type tags: F flight · A analog · M model/animal · C computational · E expert/operational/standards. AI-proposed, pending reviewer confirmation. How to read the grades.
Calculator · Earth–Moon / Earth–Mars signal delay
Light-travel time only · no relay or processing delays- Sent
— - Arrives at the crew
— - Reply sent
— - Reply arrives on Earth
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Delay = distance ÷ speed of light [1][5]. One-way Mars delays reach up to about 22 minutes (NASA: longest delays about 21–23 minutes) and that solar conjunction (about every 26 months) can cause blackouts lasting weeks [1]. Nothing you enter leaves your browser.
How it works
Radio signals travel at the speed of light, so delay = distance ÷ speed of light [1].
| Quantity | Value | Source |
|---|---|---|
| Speed of light | 299,792.458 km per second | [5] |
| Astronomical unit (au) | 149,597,870.7 km | [5] |
| Moon distance | 363,300 km (mean closest), 384,400 km (average), 405,500 km (mean farthest) | [2] |
| Mars distance | 54.6 million km (closest) to 401.4 million km (farthest) | [3] |
| Mars on a date | Earth and Mars positions from NASA JPL orbital elements (valid 1800–2050) | [4] |
For dates, the tool computes where Earth and Mars are at noon Universal Time on that day. We checked the method against NASA JPL’s Horizons ephemeris service for three dates in 2026–2027; distances agreed within 0.0002 au (about 1 second of delay).
What the delay means for medical care
- Moon: about 1.3 seconds each way, so a live video call is still workable.
- Mars: One-way delays reach up to about 22 minutes (NASA: longest delays about 21–23 minutes), and the Sun blocks signals around solar conjunction, about every 26 months, causing blackouts that can last weeks [1].
- With a 20-minute one-way delay, a question and its answer are at least 40 minutes apart. Emergency care cannot wait for the ground. The crew needs on-board skills, decision support and supplies; see the kit builder and Mission medical kits.
- NASA concludes crewed Mars missions need substantial crew and system autonomy [1].
Limits of this tool
- Light-travel time only. Real links add relay, coding and network delays.
- Mars positions are approximate (planet centers, simplified orbits); not for navigation.
- The conjunction note uses NASA’s 2° angle from its initial analysis; the fact sheet describes the angle in two ways, so its exact definition is pending verification.
Evidence profile
- Overall certainty
- ◆◆◆◆ High (proposed)
- Evidence types
- E · Expert / operational / standards
- Literature through
- 2026-10-14
- Validation
- Formulas checked against the cited sources; tool output not clinically validated
- Credit
- Educational only; no CME or other credit
Requirements referenced 0
No NASA-STD-3001 requirement maps directly to this page. See the standards quick reference.
References 5
- NASA. Mars Communications Disruption and Delay. 2023 Moon to Mars Architecture Concept Review fact sheet (2024). www.nasa.gov/wp-content/uploads/2024/01/mars-communications-… NASA E
- NASA Goddard Space Flight Center, NSSDCA. Moon Fact Sheet (semimajor axis, mean perigee and apogee). nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html NASA E
- NASA Goddard Space Flight Center, NSSDCA. Mars Fact Sheet (minimum and maximum distance from Earth). nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html NASA E
- Standish EM, Williams JG. Approximate Positions of the Planets. NASA Jet Propulsion Laboratory Solar System Dynamics (Keplerian elements, Table 1, valid 1800–2050). ssd.jpl.nasa.gov/planets/approx_pos.html NASA E
- NASA Jet Propulsion Laboratory Solar System Dynamics. Astrodynamic Parameters (speed of light, 2018 CODATA; astronomical unit, IAU 2012 Resolution B1). ssd.jpl.nasa.gov/astro_par.html NASA E
Machine-checked on 2026-10-14: each URL was fetched, each DOI's title and year matched via Crossref, PubMed IDs matched to DOIs, and every number used in a calculation was checked against the source text (abstract, NASA document, regulation or official web page). Human verification against full text is still required before review.
Article info
- Authors
- Pending (AI-assisted draft)
- Reviewer
- Pending review
- Last reviewed
- Pending review
- Literature through
- 2026-10-14
- AI-assisted
- Yes (disclosed)
- COI
- Pending
- License
- CC BY-SA 4.0 (text); code MIT
- Privacy
- Runs entirely in your browser; no inputs stored or sent
- Use
- Educational only · not for clinical decisions · Disclaimer
- Cite this version
- Pending first edition
Educational use only · not medical advice · not for clinical decisions · Disclaimer · CC BY-SA 4.0