IPAS: InterPlanetary Atomic Swaps
InterPlanetary Atomic Swaps (IPAS) extend hash time-locked contracts across the Earth-Mars communication delay — enabling trustless cross-planetary commerce, remittance, and investment without intermediaries.
Abstract
This paper introduces IPAS — the InterPlanetary Atomic Swap — an extension of hash time-locked contracts (HTLCs) for trustless value transfer between blockchains operating on different planets. We demonstrate that the cryptographic properties of HTLCs are inherently distance-agnostic: the preimage-based atomicity guarantee holds regardless of the communication latency between counterparties. By extending timelock parameters to accommodate the 4–24 minute Earth-Mars light-speed delay, solar conjunction blackout periods, and operational response margins, IPAS enables cross-planetary commerce, remittance, and investment without any trusted intermediary.
The construction requires no protocol changes to existing HTLC implementations. The first BTC↔MARS atomic swap completed on mainnet on April 12, 2026, using timelocks of 4 and 8 hours. IPAS proposes extending these to 72 and 144 hours for Earth-Mars operations — a configuration change, not a protocol change. The fundamental guarantee is identical: either both sides complete, or both sides refund.
1. The Problem: Exchanging Value Across Planetary Distances
Every financial transaction in human history has occurred within a single light-speed boundary. A wire transfer between New York and Tokyo takes seconds of propagation delay, masked by hours or days of institutional processing. A Bitcoin transaction confirms globally within 10 minutes because every node on the planet can communicate within milliseconds.
Mars breaks this assumption. The one-way light-speed delay between Earth and Mars ranges from approximately 3 minutes at closest approach to 22 minutes at greatest distance, with an average of about 13 minutes. Round-trip communication takes 6 to 44 minutes. During solar conjunction — roughly every 26 months, lasting about two weeks — radio communication is blocked entirely.
This delay is not a network engineering problem. It is a physical law. No protocol optimization, no relay satellite, no compression algorithm can make a photon travel faster. Any financial infrastructure designed for Mars must treat latency not as a bug to be fixed but as a fundamental parameter to be incorporated.
Centralized exchanges cannot operate across this gap. An exchange matching engine that takes 13 minutes to acknowledge an order — and 13 more minutes to confirm the fill — is not a viable trading platform. Custodial bridges are worse: depositing funds with an intermediary 225 million kilometers away, trusting their solvency across a communication channel that goes dark for two weeks every two years, is a risk profile no rational actor would accept.
What we need is a protocol where both parties can commit to a trade, execute it asynchronously, and be guaranteed a fair outcome regardless of how long the messages take to arrive.
2. Why HTLCs Survive Latency
A Hash Time-Locked Contract has two properties that make it uniquely suited to high-latency environments.
First, the hash lock is atemporal. The preimage — the secret that unlocks the contract — does not expire, degrade, or change with distance. A preimage generated on Mars and revealed on the Bitcoin blockchain is just as valid whether an observer detects it in 3 minutes (close approach) or 22 minutes (far approach) or 14 days later (post-conjunction). The hash function doesn’t know where the preimage came from. It verifies instantly, deterministically, and identically on every node.
Second, the time lock uses block height, not wall-clock time. OP_CHECKLOCKTIMEVERIFY compares the transaction’s nLockTime against the embedded locktime value — both expressed as block heights on their respective chains. Earth’s clock and Mars’s clock need not agree. Each chain advances at its own pace, and the refund path becomes available when that chain’s own tip reaches the specified height. Clock synchronization between planets is irrelevant.
These two properties mean that an HTLC constructed for a 4-hour settlement window works identically whether the counterparties are in the same room or on different planets. The only adaptation required is extending the timelock duration to absorb the communication delay and provide adequate safety margins.
3. The IPAS Protocol
3.1 Participants and Roles
An IPAS transaction involves two parties:
The Mars-side party holds Marscoin and wants to direct Bitcoin to an address on Earth. This party generates the preimage and initiates the swap.
The Earth-side party holds Bitcoin and wants to direct Marscoin to an address on Mars. This party funds the Bitcoin HTLC after verifying the Marscoin HTLC on-chain.
Note a critical design choice: neither party is required to receive the funds themselves. The HTLC’s claim path only verifies a signature against a specific public key and a preimage against a specific hash. The public key can belong to anyone the swap participant designates: a supplier, a family member, a governance treasury, an institution.
3.2 The Destination Address Insight
This is what makes IPAS a vehicle for commerce rather than merely speculation.
Consider: a colonist on Mars needs to pay an Earth-based supplier for equipment. The colonist holds MARS. The supplier wants Bitcoin. The colonist creates an IPAS offer specifying the supplier’s Bitcoin address as the claim destination. An Earth-based taker — perhaps a Marscoin investor — accepts the offer and funds the Bitcoin HTLC. When the swap completes, the supplier receives Bitcoin directly. The colonist sold MARS for real-world goods. The taker acquired MARS exposure in the Martian economy.
Three parties, two blockchains, two planets, zero intermediaries.
The same construction enables interplanetary remittance. An Earth-based parent takes a MARS offer and specifies the child’s Marscoin address on Mars as the claim destination. The parent’s Bitcoin goes to the maker, the MARS goes to the child. No wire service, no bank, no Western Union with a 13-minute hold time.
It enables interplanetary investment. An institution on Earth acquires MARS through IPAS and directs the output to a Martian Republic governance treasury — funding infrastructure development on Mars through a trustless on-chain transaction.
In each case, the HTLC is indifferent to the intent. It enforces the cryptographic contract: preimage reveals bind both sides, and timelocks ensure refunds. What the humans choose to do with those mechanics — pay suppliers, support family, fund governance — is their sovereign decision.
3.3 Extended Timelocks
The timelock parameters for IPAS must account for delay sources that do not exist in terrestrial atomic swaps:
Light-speed propagation. A transaction broadcast from Mars takes 3–22 minutes to reach Earth’s Bitcoin network. Round-trip is 6–44 minutes. The preimage, once revealed on the Bitcoin chain, takes equally long to become visible on Mars.
Block confirmation variance. Bitcoin’s 10-minute target block time has high variance — individual blocks may take 1 minute or 60 minutes. Marscoin’s 123-second blocks have lower variance but the same statistical distribution. Multiple confirmations compound the variance.
Operational response time. On Earth, a wallet detects a preimage reveal and constructs a claim transaction within seconds. On Mars, where computing resources may be shared across life support, communications, and scientific workloads, the response window may be hours rather than seconds.
Solar conjunction blackouts. Approximately every 26 months, the Sun blocks Earth-Mars radio communication for about two weeks. Any swap initiated before conjunction with a timelock shorter than the blackout will fail — the Mars party cannot observe preimage reveals on the Bitcoin chain during blackout.
A conservative IPAS timelock design:
| Scenario | BTC Timelock | MARS Timelock | Safety Gap | Capital Lockup |
|---|---|---|---|---|
| Close approach (~3 min delay) | 48 hours | 96 hours | 48 hours | Up to 4 days |
| Average distance (~13 min delay) | 72 hours | 144 hours | 72 hours | Up to 6 days |
| Far approach (~22 min delay) | 96 hours | 192 hours | 96 hours | Up to 8 days |
| Pre-conjunction (with margin) | 504 hours (21 days) | 672 hours (28 days) | 168 hours (7 days) | Up to 4 weeks |
The asymmetry rule remains: the party who funds last (Earth-side, with BTC) must be able to refund first. This prevents the Mars party from claiming BTC at the last moment and then refunding MARS before the Earth party can extract the preimage — the same race condition that the 4-hour gap prevents in terrestrial swaps, now scaled to interplanetary margins.
For a civilization where physical cargo takes months to travel between planets, a 6-day financial settlement is effectively instant.
3.4 Offer Propagation
IPAS offers originate on the Marscoin network (broadcast via ElectrumX relay) and must propagate to Earth for takers to discover them. In the current Electrum-Mars architecture, ElectrumX servers gossip offers to peers. For IPAS, this gossip crosses the interplanetary link — a Marscoin ElectrumX server on Mars relays to a Marscoin ElectrumX server on Earth (or vice versa) over whatever communication infrastructure connects the two planets.
The offer format requires no changes. An IPAS offer is a standard atomic swap offer with longer expiry times. Earth-side Electrum-Mars wallets display it identically to any other offer, with the swap engine automatically detecting the extended timelocks and adjusting its monitoring intervals.
A future enhancement might add an ipas: true flag to the offer format, signaling the extended settlement timeline and allowing wallet UIs to display estimated completion times, conjunction warnings, and orbital-position-aware delay estimates.
4. Infrastructure Requirements
4.1 The Delayed Blockchain Mirror
Both planets would naturally maintain batched, delayed copies of each other’s blockchain. This is not a dependency — neither chain needs the other for its own consensus. It is an observation layer: Mars watches Bitcoin, Earth watches Marscoin, each with the inherent light-speed delay.
Mars maintaining a Bitcoin mirror. The Mars settlement receives Bitcoin block data via whatever deep-space communication link connects the two planets. The minimum viable relay is block headers only — 80 bytes per block, approximately 4.7 KB per hour of Bitcoin blocks. A settlement receiving even intermittent data links could maintain a synchronized header chain. With headers, an SPV client on Mars can verify that a claim transaction exists in a block without downloading the full block. A more robust relay transmits full blocks — at Bitcoin’s current average of ~1.5 MB per block and ~6 blocks per hour, this is approximately 9 MB per hour, well within the capacity of any communication link designed to support a human settlement.
The key point: Mars doesn’t use the Bitcoin blockchain. It doesn’t mine Bitcoin. It doesn’t submit Bitcoin transactions locally. It simply observes — and that observation is all IPAS needs to extract a preimage from a claim transaction.
Earth maintaining a Marscoin mirror. The same logic applies in reverse. Earth-based ElectrumX servers already index the Marscoin chain. For IPAS, they receive Marscoin block data from Mars-based full nodes via the interplanetary link. Since Marscoin is a smaller chain with 2-minute blocks and minimal block sizes, relaying full Marscoin blocks to Earth requires trivial bandwidth. Earth-side takers verify that the Mars-side maker has funded the MARS HTLC by querying their local delayed copy of the Marscoin chain.
Both directions are symmetrical. Each planet maintains a delayed mirror of the other’s chain. Neither depends on the other. Both observe. This architecture means that IPAS participants never need to trust a relay operator — they can verify any claim against their own local copy of the counterparty’s blockchain, delayed by nothing more than the speed of light.
4.3 Conjunction Handling
During solar conjunction (~2 weeks every ~26 months), no data traverses the Earth-Mars link. IPAS wallets must be conjunction-aware:
Pre-conjunction offers should carry timelocks that exceed the blackout duration plus safety margin. The wallet UI should warn makers: “Solar conjunction begins in 10 days. This offer’s timelocks will be set to 28/35 days to span the blackout period.”
Mid-conjunction behavior: Both parties’ wallets continue monitoring their local chains. If a claim occurs on one chain during conjunction, the preimage exists in the blockchain data and will be discovered by the other party when communication resumes. The extended timelock ensures neither party’s refund activates during the blackout.
Post-conjunction synchronization: When communication resumes, both parties’ wallets sync block data and resume the swap worker. Any pending preimage extraction completes normally.
4.4 Multiple Communication Paths
To mitigate relay censorship or failure, the Mars settlement should receive Bitcoin block data through multiple independent channels — direct deep-space radio, laser communication links, and potentially store-and-forward via orbital relay satellites. No single communication provider should be able to prevent the Mars party from learning about preimage reveals on the Bitcoin chain.
5. Economic Implications
5.1 Interplanetary Commerce
IPAS transforms Marscoin from a speculative asset into a functional medium of exchange for Earth-Mars trade. A Mars colony that produces unique goods — scientific data, mineral samples, intellectual property, even tourism vouchers — can sell them for Bitcoin directed to Earth-side suppliers of equipment, materials, or services. The colonist’s MARS balance decreases, the supplier’s Bitcoin balance increases, and the exchange rate is set by the counterparties themselves — no exchange listing, no market maker, no regulatory intermediary.
5.2 Remittance
Earth-to-Mars remittance through IPAS is structurally identical to how hawala networks operate today — except trustless. A parent on Earth sends value to a child on Mars by taking a MARS offer. The parent pays Bitcoin; the child receives Marscoin. The Mars-side maker facilitates the transfer by providing liquidity. In hawala, the intermediary is trusted. In IPAS, the intermediary is replaced by an HTLC.
5.3 Capital Formation and the Funding Problem
This may be the most consequential implication of IPAS. One of the persistent challenges of Mars colonization is funding: who pays for the ships, the habitats, the supplies? Government budgets are unreliable. Private investment requires returns. Philanthropy doesn’t scale.
IPAS introduces a different mechanism. A Mars colony that has built economic value — scientific discoveries, mineral extraction rights, manufactured goods, intellectual property, governance participation rights — can convert that value into Earth-side purchasing power immediately through atomic swaps. Martian wealth can buy equipment, supplies, even fund spacecraft construction on Earth, by locking MARS and directing the BTC output to the suppliers’ addresses. The colony doesn’t need a bank account on Earth. It doesn’t need a wire service. It needs only a counterparty willing to trade BTC for MARS — and the Auto-Maker feature means that counterparty can be any Earth-side Marscoin holder running an Electrum-Mars wallet.
In the other direction, Earth-side capital can flow to Mars almost directly. An investor, an institution, or a government aid program takes IPAS offers, acquiring MARS that funds Martian Republic governance, infrastructure projects, or individual colonists’ accounts. The capital arrives on Mars as spendable Marscoin within the IPAS settlement window — days, not months.
This is not speculation about a distant future. It is a concrete protocol extension of technology that works today on mainnet. The day a Starship carries The Seed to Mars, the colony has a working mechanism to trade with Earth from the moment it powers on.
5.4 Price Discovery
IPAS offers naturally create a cross-planetary order book. The BTC/MARS exchange rate is set by makers and takers based on their own assessment of value. Over time, this distributed price discovery mechanism produces a market rate for interplanetary trade — the first such rate in human history, emerging from peer-to-peer transactions rather than institutional proclamation.
6. Relationship to Existing Work
IPAS builds on a lineage of cross-chain exchange research:
Tier Nolan’s atomic swap proposal (2013) first described the HTLC-based cross-chain exchange pattern on BitcoinTalk. The construction has been refined but not fundamentally changed in thirteen years.
Decred atomic swap tools (2017) provided the first widely used implementation, demonstrating BTC↔DCR swaps with command-line tools.
Lightning Network HTLCs use the same construction for multi-hop payment routing. Each hop in a Lightning payment is an HTLC with decreasing timelocks — the same asymmetry principle used in IPAS.
Marscoin’s Electrum-Mars atomic swap (2026) is, to our knowledge, the first wallet-integrated implementation for a Litecoin-derived chain, and the first to include a decentralized order book, auto-maker, and the IPAS extension described here.
The novel contribution of IPAS is not the HTLC itself — that is proven technology. The contribution is the rigorous analysis of its behavior under interplanetary latency conditions, the timelock parameter design for various orbital configurations, the conjunction-aware protocol extensions, and the economic implications of trustless cross-planetary value transfer.
7. Conclusion
The InterPlanetary Atomic Swap is not science fiction. Every component of the protocol has been demonstrated on mainnet with real money. The HTLC construction works. The preimage extraction works. The timelock refund works. What remains is extending the timelock parameters and building conjunction-aware wallet UX — engineering work on a proven cryptographic foundation.
The deeper insight is that HTLCs are accidentally interplanetary. They were designed for a world where both parties are on the same planet, operating on the same blockchains, with sub-second communication. But nothing in the construction requires those conditions. The hash doesn’t care about distance. The timelock doesn’t care about latency. The preimage doesn’t degrade with distance. These are properties of mathematics, not of geography.
When someone boards a Starship carrying The Seed — a bootable image containing the entire Marscoin infrastructure — they carry the ability to trade trustlessly with Earth from the moment they power on. The blockchains on both planets enforce the contracts. The speed of light delivers the preimage. And the mathematics guarantees that either both parties get what they agreed to, or neither loses anything.
IPAS. InterPlanetary Atomic Swap. Like IPFS before it, the name states the ambition. Unlike most ambitions in cryptocurrency, this one is backed by working code and mainnet transactions.
This paper was developed by the Marscoin Foundation as part of the broader Quantum Upgrade Proposal research program. For the underlying HTLC construction, see Hash Time-Locked Contracts. For the current Earth-based implementation, see Atomic Swaps in Electrum-Mars. For the first mainnet swap report, see the April 12, 2026 announcement. Comments and discussion: martianrepublic.org.
